(Slip Opinion)              OCTOBER TERM, 2014                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

      TEVA PHARMACEUTICALS USA, INC., ET AL. v. 

               SANDOZ, INC., ET AL. 


CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
                THE FEDERAL CIRCUIT

  No. 13–854.      Argued October 15, 2014—Decided January 20, 2015
Petitioners, Teva Pharmaceuticals (and related firms), own a patent
  that covers a manufacturing method for the multiple sclerosis drug
  Copaxone. When respondents, Sandoz, Inc. (and other firms), tried to
  market a generic version of the drug, Teva sued them for patent in­
  fringement. Sandoz countered that the patent was invalid. Specifi­
  cally, Sandoz argued that the claim that Copaxone’s active ingredient
  had “a molecular weight of 5 to 9 kilodaltons” was fatally indefinite,
  see 35 U. S. C. §112 ¶2, because it did not state which of three meth­
  ods of calculation—the weight of the most prevalent molecule, the
  weight as calculated by the average weight of all molecules, or weight
  as calculated by an average in which heavier molecules count for
  more—was used to determine that weight. After considering conflict­
  ing expert evidence, the District Court concluded that the patent
  claim was sufficiently definite and the patent was thus valid. As rel­
  evant here, it found that in context a skilled artisan would under­
  stand that the term “molecular weight” referred to molecular weight
  as calculated by the first method. In finding the “molecular weight”
  term indefinite and the patent invalid on appeal, the Federal Circuit
  reviewed de novo all aspects of the District Court’s claim construc­
  tion, including the District Court’s determination of subsidiary facts.
Held: When reviewing a district court’s resolution of subsidiary factual
 matters made in the course of its construction of a patent claim, the
 Federal Circuit must apply a “clear error,” not a de novo, standard of
 review. Pp. 4–16.
    (a) Federal Rule of Civil Procedure 52(a)(6) states that a court of
 appeals “must not . . . set aside” a district court’s “[f]indings of fact”
 unless they are “clearly erroneous.” It sets out a “clear command,”
2       TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                                    Syllabus

    Anderson v. Bessemer City, 470 U. S. 564, 574, and “does not make
    exceptions or . . . exclude certain categories of factual findings” from
    the court of appeals’ obligation, Pullman-Standard v. Swint, 456
    U. S. 273, 287. The Rule thus applies to both subsidiary and ulti­
    mate facts. Ibid. And the function of an appeals court reviewing the
    findings of a “ ‘district court sitting without a jury . . . is not to decide
    factual issues de novo.’ ” Anderson, supra, at 573. Even if exceptions
    to the Rule were permissible, there is no convincing ground for creat­
    ing an exception here. Markman v. Westview Instruments, Inc., 517
    U. S. 370, neither created, nor argued for, such an exception. There,
    the Court held that the ultimate question of claim construction is for
    the judge, not the jury, id., at 372, but it did not thereby create an ex­
    ception from the ordinary rule governing appellate review of factual
    matters. Instead, the Court pointed out that a judge, in construing a
    patent claim, is engaged in much the same task as the judge would
    be in construing other written instruments, such as deeds, contracts,
    or tariffs. Id., at 384, 386, 388, 389. Construction of written instru­
    ments often presents a “question solely of law,” at least when the
    words in those instruments are “used in their ordinary meaning.”
    Great Northern R. Co. v. Merchants Elevator Co., 259 U. S. 285, 291.
    But if a written instrument uses “technical words or phrases not
    commonly understood,” id., at 292, those words may give rise to a fac­
    tual dispute. If so, extrinsic evidence may help to “establish a usage
    of trade or locality.” Ibid. And in that circumstance, the “determina­
    tion of the matter of fact” will “preced[e]” the “function of construc­
    tion.” Ibid.
       The Markman Court also recognized that courts will sometimes
    have to resolve subsidiary factual disputes in patent construction;
    Rule 52 requires appellate courts to review such disputes under the
    “clearly erroneous” standard. Application of this standard is further
    supported by precedent and by practical considerations. Clear error
    review is “particularly” important in patent cases because a district
    court judge who has presided over, and listened to, the entire pro­
    ceeding has a comparatively greater opportunity to gain the neces­
    sary “familiarity with specific scientific problems and principles,”
    Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U. S. 605,
    610, than an appeals court judge who must read a written transcript
    or perhaps just those portions referenced by the parties. Pp. 4–8.
       (b) Arguments to the contrary are unavailing. Sandoz claims that
    separating “factual” from “legal” questions may be difficult and, like
    the Federal Circuit, posits that it is simpler for the appellate court to
    review the entirety of the district court’s claim construction de novo
    than to apply two separate standards. But courts of appeals have
    long been able to separate factual from legal matters, see, e.g., First
                     Cite as: 574 U. S. ____ (2015)                      3

                                Syllabus

  Options of Chicago, Inc. v. Kaplan, 514 U. S. 938, 947–948, and the
  Federal Circuit’s efforts to treat factual findings and legal conclu­
  sions similarly have brought with them their own complexities. As
  for Sandoz’s argument that “clear error” review will bring about less
  uniformity, neither the Circuit nor Sandoz has shown that divergent
  claim construction stemming from divergent findings of fact on sub­
  sidiary matters should occur more than occasionally. Pp. 8–11.
     (c) This leaves the question of how the clear error standard should
  be applied when reviewing subsidiary factfinding in patent claim
  construction. When the district court reviews only evidence intrinsic
  to the patent, the judge’s determination is solely a determination of
  law, and the court of appeals will review that construction de novo.
  However, where the district court needs to consult extrinsic evidence
  in order to understand, for example, the background science or the
  meaning of a term in the relevant art during the relevant time peri­
  od, and where those subsidiary facts are in dispute, courts will need
  to make subsidiary factual findings about the extrinsic evidence. The
  district judge, after deciding the factual dispute, will then interpret
  the patent claim in light of the facts as he has found them. The ulti­
  mate construction of the claim is a legal conclusion that the appellate
  court can review de novo. But to overturn the judge’s resolution of an
  underlying factual dispute, the appellate court must find that the
  judge, in respect to those factual findings, has made a clear error.
  Pp. 11–14.
     (d) Here, for example, the District Court made a factual finding,
  crediting Teva’s expert’s account, and thereby rejecting Sandoz’s ex­
  pert’s contrary explanation, about how a skilled artisan would under­
  stand the way in which a curve created from chromatogram data re­
  flects molecular weights. Based on that factual finding, the District
  Court reached the legal conclusion that figure 1 did not undermine
  Teva’s argument that molecular weight referred to the first method of
  calculating molecular weight. When the Federal Circuit reviewed the
  District Court’s decision, it did not accept Teva’s expert’s explanation,
  and it failed to accept that explanation without finding that the Dis­
  trict Court’s contrary determination was “clearly erroneous.” The
  Federal Circuit erred in failing to review this factual finding only for
  clear error. Teva asserts that there are two additional instances in
  which the Federal Circuit rejected the District Court’s factual find­
  ings without concluding that they were clearly erroneous; those mat­
  ters are left for the Federal Circuit to consider on remand. Pp. 14–
  16.
723 F. 3d 1363, vacated and remanded.

  BREYER, J., delivered the opinion of the Court, in which ROBERTS,
4    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                             Syllabus

C. J., and SCALIA, KENNEDY, GINSBURG, SOTOMAYOR, and KAGAN, JJ.,
joined. THOMAS, J., filed a dissenting opinion, in which ALITO, J.,
joined.
                        Cite as: 574 U. S. ____ (2015)                              1

                             Opinion of the Court

     NOTICE: This opinion is subject to formal revision before publication in the
     preliminary print of the United States Reports. Readers are requested to
     notify the Reporter of Decisions, Supreme Court of the United States, Wash­
     ington, D. C. 20543, of any typographical or other formal errors, in order
     that corrections may be made before the preliminary print goes to press.


SUPREME COURT OF THE UNITED STATES
                                   _________________

                                   No. 13–854
                                   _________________


     TEVA PHARMACEUTICALS USA, INC., ET AL., 

        PETITIONERS v. SANDOZ, INC., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FEDERAL CIRCUIT

                               [January 20, 2015]


   JUSTICE BREYER delivered the opinion of the Court.
   In Markman v. Westview Instruments, Inc., 517 U. S.
370 (1996), we explained that a patent claim is that “por­
tion of the patent document that defines the scope of the
patentee’s rights.” Id., at 372. We held that “the con­
struction of a patent, including terms of art within its
claim,” is not for a jury but “exclusively” for “the court” to
determine. Ibid. That is so even where the construction
of a term of art has “evidentiary underpinnings.” Id., at
390.
   Today’s case involves claim construction with “eviden­
tiary underpinnings.” See Part III, infra. And, it requires
us to determine what standard the Court of Appeals
should use when it reviews a trial judge’s resolution of an
underlying factual dispute. Should the Court of Appeals
review the district court’s factfinding de novo as it would
review a question of law? Or, should it review that fact-
finding as it would review a trial judge’s factfinding in
other cases, namely by taking them as correct “unless
clearly erroneous?” See Fed. Rule Civ. Proc. 52(a)(6). We
hold that the appellate court must apply a “clear error,”
2    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

not a de novo, standard of review.
                                I
   The basic dispute in this case concerns the meaning of
the words “molecular weight” as those words appear in a
patent claim. The petitioners, Teva Pharmaceuticals
(along with related firms), own the relevant patent. The
patent covers a manufacturing method for Copaxone, a
drug used to treat multiple sclerosis. The drug’s active
ingredient, called “copolymer-1,” is made up of molecules
of varying sizes. App. 1143a. And the relevant claim
describes that ingredient as having “a molecular weight of
5 to 9 kilodaltons.” Id., at 1145a.
   The respondents, Sandoz, Inc. (and several other firms),
tried to market a generic version of Copaxone. Teva sued
Sandoz for patent infringement. 810 F. Supp. 2d 578, 581
(SDNY 2011). Sandoz defended the suit by arguing that
the patent was invalid. Ibid. The Patent Act requires
that a claim “particularly poin[t] out and distinctly clai[m]
the subject matter which the applicant regards as his
invention.” 35 U. S. C. §112 ¶2 (2006 ed.); see Nautilus,
Inc. v. Biosig Instruments, Inc., 572 U. S. ___, ___, n. 1
(2014) (slip op., at 3, n. 1)). The phrase “molecular weight
of 5 to 9 kilodaltons,” said Sandoz, did not satisfy this
requirement.
   The reason that the phrase is fatally indefinite, Sandoz
argued, is that, in the context of this patent claim, the
term “molecular weight” might mean any one of three
different things. The phrase might refer (1) to molecular
weight as calculated by the weight of the molecule that is
most prevalent in the mix that makes up copolymer-1.
(The scientific term for molecular weight so calculated is,
we are told, “peak average molecular weight.”) The phrase
might refer (2) to molecular weight as calculated by taking
all the different-sized molecules in the mix that makes up
copolymer-1 and calculating the average weight, i.e.,
                  Cite as: 574 U. S. ____ (2015)            3

                      Opinion of the Court

adding up the weight of each molecule and dividing by the
number of molecules. (The scientific term for molecular
weight so calculated is, we are told, “number average
molecular weight.”) Or, the phrase might refer (3) to
molecular weight as calculated by taking all the different-
sized molecules in the mix that makes up copolymer-1 and
calculating their average weight while giving heavier
molecules a weight-related bonus when doing so. (The
scientific term for molecular weight so calculated, we are
told, is “weight average molecular weight.”) See 723 F. 3d
1363, 1367 (CA Fed. 2013); App. 124a. In Sandoz’s view,
since Teva’s patent claim does not say which method of
calculation should be used, the claim’s phrase “molecular
weight” is indefinite, and the claim fails to satisfy the
critical patent law requirement.
   The District Court, after taking evidence from experts,
concluded that the patent claim was sufficiently definite.
Among other things, it found that in context a skilled
artisan would understand that the term “molecular
weight” referred to molecular weight as calculated by the
first method, i.e., “peak average molecular weight.” 810
F. Supp. 2d, at 596; see Nautilus, supra, at ___ (slip op., at
12) (“[T]he definiteness inquiry trains on the understand­
ing of a skilled artisan at the time of the patent applica­
tion”). In part for this reason, the District Court held the
patent valid. 810 F. Supp. 2d, at 596.
   On appeal, the Federal Circuit held to the contrary. It
found that the term “molecular weight” was indefinite.
And it consequently held the patent invalid. 723 F. 3d, at
1369. In reaching this conclusion, the Federal Circuit
reviewed de novo all aspects of the District Court’s claim
construction, including the District Court’s determination
of subsidiary facts. Id., at 1369, 1373; see also Light-
ing Ballast Control LLC v. Philips Electronics North
Am. Corp., 744 F. 3d 1272, 1276–1277 (CA Fed. 2014) (en
banc) (reaffirming de novo review of district court claim
4    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                      Opinion of the Court

construction).
   Teva filed a petition for certiorari. And we granted that
petition. The Federal Circuit reviews the claim construc­
tion decisions of federal district courts throughout the
Nation, and we consequently believe it important to clarify
the standard of review that it must apply when doing so.
                               II

                               A

   Federal Rule of Civil Procedure 52(a)(6) states that a
court of appeals “must not . . . set aside” a district court’s
“[f ]indings of fact” unless they are “clearly erroneous.” In
our view, this rule and the standard it sets forth must
apply when a court of appeals reviews a district court’s
resolution of subsidiary factual matters made in the
course of its construction of a patent claim. We have made
clear that the Rule sets forth a “clear command.” Ander-
son v. Bessemer City, 470 U. S. 564, 574 (1985). “It does
not make exceptions or purport to exclude certain catego­
ries of factual findings from the obligation of a court of
appeals to accept a district court’s findings unless clearly
erroneous.” Pullman-Standard v. Swint, 456 U. S. 273,
287 (1982). Accordingly, the Rule applies to both subsidi­
ary and ultimate facts. Ibid. And we have said that,
when reviewing the findings of a “ ‘district court sitting
without a jury, appellate courts must constantly have in
mind that their function is not to decide factual issues
de novo.’ ” Anderson, supra, at 573 (quoting Zenith Radio
Corp. v. Hazeltine Research, Inc., 395 U. S. 100, 123
(1969)).
   Even if exceptions to the Rule were permissible, we
cannot find any convincing ground for creating an excep­
tion to that Rule here. The Rules Advisory Committee
pointed out that, in general, exceptions “would tend to
undermine the legitimacy of the district courts . . . , multi­
ply appeals . . . , and needlessly reallocate judicial author­
                 Cite as: 574 U. S. ____ (2015)           5

                     Opinion of the Court

ity.” Advisory Committee’s 1985 Note on subd. (a) of Fed.
Rule Civ. Proc. 52, 28 U. S. C. App., pp. 908–909; see also
Anderson, supra, at 574–575 (de novo review of fac-
tual findings “would very likely contribute only negligibly”
to accuracy “at a huge cost in diversion of judicial
resources”).
   Our opinion in Markman neither created, nor argued
for, an exception to Rule 52(a). The question presented in
that case was a Seventh Amendment question: Should a
jury or a judge construe patent claims? 517 U. S., at 372.
We pointed out that history provides no clear answer. Id.,
at 388. The task primarily involves the construction of
written instruments. Id., at 386, 388, 389. And that task
is better matched to a judge’s skills. Id., at 388 (“The
construction of written instruments is one of those things
that judges often do and are likely to do better than jurors
unburdened by training in exegesis”). We consequently
held that claim construction falls “exclusively within the
province of the court,” not that of the jury. Id., at 372.
   When describing claim construction we concluded that it
was proper to treat the ultimate question of the proper
construction of the patent as a question of law in the way
that we treat document construction as a question of law.
Id., at 388–391. But this does not imply an exception to
Rule 52(a) for underlying factual disputes. We used the
term “question of law” while pointing out that a judge, in
construing a patent claim, is engaged in much the same
task as the judge would be in construing other written
instruments, such as deeds, contracts, or tariffs. Id., at
384, 386, 388, 389; see also Motion Picture Patents Co. v.
Universal Film Mfg. Co., 243 U. S. 502, 510 (1917) (patent
claims are “aptly likened to the description in a deed,
which sets the bounds to the grant which it contains”);
Goodyear Dental Vulcanite Co. v. Davis, 102 U. S. 222, 227
(1880) (analogizing patent construction to the construction
of other written instruments like contracts). Construction
6    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

of written instruments often presents a “question solely of
law,” at least when the words in those instruments are
“used in their ordinary meaning.” Great Northern R. Co.
v. Merchants Elevator Co., 259 U. S. 285, 291 (1922). But
sometimes, say when a written instrument uses “technical
words or phrases not commonly understood,” id., at 292,
those words may give rise to a factual dispute. If so, ex­
trinsic evidence may help to “establish a usage of trade or
locality.” Ibid. And in that circumstance, the “determina­
tion of the matter of fact” will “preced[e]” the “function of
construction.” Ibid.; see also 12 R. Lord, Williston on
Contracts §§34:1, p. 2, 34:19, p. 174 (4th ed. 2012) (In
contract interpretation, the existence of a “usage”—a
“practice or method” in the relevant industry—“is a ques­
tion of fact” (internal quotation marks omitted)). This
factual determination, like all other factual determina­
tions, must be reviewed for clear error. See Pullman-
Standard, supra at 287 (The Rule does not “exclude cer­
tain categories of factual findings” and applies to both
“subsidiary” and “ultimate” facts (internal quotation
marks omitted)).
   Accordingly, when we held in Markman that the ulti­
mate question of claim construction is for the judge and
not the jury, we did not create an exception from the ordi­
nary rule governing appellate review of factual matters.
Markman no more creates an exception to Rule 52(a) than
would a holding that judges, not juries, determine equit­
able claims, such as requests for injunctions. A conclusion
that an issue is for the judge does not indicate that Rule
52(a) is inapplicable. See Fed. Rule Civ. Proc. 52 (setting
the standard of review for “[Factual] Findings and Conclu­
sions by the Court” (emphasis added)).
   While we held in Markman that the ultimate issue of
the proper construction of a claim should be treated as a
question of law, we also recognized that in patent con­
struction, subsidiary factfinding is sometimes necessary.
                  Cite as: 574 U. S. ____ (2015)            7

                      Opinion of the Court

Indeed, we referred to claim construction as a practice
with “evidentiary underpinnings,” a practice that “falls
somewhere between a pristine legal standard and a simple
historical fact.” 517 U. S., at 378, 388, 390. We added
that sometimes courts may have to make “credibility
judgments” about witnesses. Id., at 389. In other words,
we recognized that courts may have to resolve subsidiary
factual disputes. And, as explained above, the Rule re­
quires appellate courts to review all such subsidiary fac­
tual findings under the “clearly erroneous” standard.
   Precedent further supports application of the “clearly
erroneous” standard. Before the creation of the Federal
Circuit, the Second Circuit explained that in claim con­
struction, the subsidiary “question . . . of how the art un-
derstood the term . . . was plainly a question of fact; and
unless the [district court’s] finding was ‘clearly erroneous,’
we are to take” it “as controlling.” Harries v. Air King
Products, Co., 183 F. 2d 158, 164 (CA2 1950) (L. Hand,
C. J.). We have said the same as to subsidiary factual
findings concerning other patent law inquiries, including
“obviousness.” Dennison Mfg. Co. v. Panduit Corp., 475
U. S. 809, 811 (1986) (per curiam) (“subsidiary determina­
tions of the District Court” subject to Rule 52(a)’s clear
error standard).
   Finally, practical considerations favor clear error re­
view. We have previously pointed out that clear error
review is “particularly” important where patent law is at
issue because patent law is “a field where so much de­
pends upon familiarity with specific scientific problems
and principles not usually contained in the general store­
house of knowledge and experience.” Graver Tank & Mfg.
Co. v. Linde Air Products Co., 339 U. S. 605, 610 (1950). A
district court judge who has presided over, and listened to,
the entirety of a proceeding has a comparatively greater
opportunity to gain that familiarity than an appeals court
judge who must read a written transcript or perhaps just
8    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

those portions to which the parties have referred. Cf.
Lighting Ballast, 744 F. 3d, at 1311 (O’Malley, J., dissent­
ing) (Federal Circuit judges “lack the tools that district
courts have available to resolve factual disputes fairly and
accurately,” such as questioning the experts, examining
the invention in operation, or appointing a court-appointed
expert); Anderson, 470 U. S., at 574 (“The trial judge’s
major role is the determination of fact, and with experi­
ence in fulfilling that role comes expertise”).
                              B
   Sandoz argues that claim construction mostly consists of
construing a set of written documents that do not give rise
to subsidiary factual disputes. Tr. of Oral Arg. 39. It adds
that separating “factual” from “legal” questions is often
difficult. And Sandoz, like the Federal Circuit itself,
argues that it is simpler for that appellate court to review
the entirety of the district court’s claim construction de
novo rather than to apply two separate standards. Id., at
38; see also Lighting Ballast, supra, at 1284 (criticizing
clear error review in part because of the purportedly diffi­
cult task of “disentangling” fact from law).
   But even were we free to ignore the Federal Rule (which
we are not), we would not find this argument convincing.
Courts of appeals have long found it possible to separate
factual from legal matters. See, e.g., First Options of
Chicago, Inc. v. Kaplan, 514 U. S. 938, 947–948 (1995)
(review of factual findings for clear error and legal conclu­
sions de novo is the “ordinary” standard for courts of ap­
peals). At the same time, the Federal Circuit’s efforts to
treat factual findings and legal conclusions similarly have
brought with them their own complexities. See e.g., Cybor
Corp. v. FAS Technologies, Inc., 138 F. 3d 1448, 1454 (CA
Fed. 1998) (en banc) (claim construction does not involve
“factual evidentiary findings” (citation and internal quota­
tion marks omitted)); Lighting Ballast, supra, at 1284
                 Cite as: 574 U. S. ____ (2015)            9

                     Opinion of the Court

(claim construction has “arguably factual aspects”); Dow
Jones & Co. v. Ablaise Ltd., 606 F. 3d 1338, 1344–1345
(CA Fed. 2010) (“[T]his court,” while reviewing claim
construction without deference, “takes into account the
views of the trial judge”); Nazomi Communications Inc., v.
Arm Holdings, PLC, 403 F. 3d 1364, 1371 (CA Fed. 2005)
(“[C]ommon sense dictates that the trial judge’s view will
carry weight” (citation and internal quotation marks
omitted)); Lightning Ballast, supra, at 1294 (Lourie, J.,
concurring) (we should “rarely” overturn district court’s
true subsidiary factfinding; “we should, and do, give proper
informal deference to the work of judges of a subordinate
tribunal”); Cybor, supra, at 1480 (opinion of Newman, J.)
(“By continuing the fiction that there are no facts to be
found in claim interpretations, we confound rather than
ease the litigation process”); see also Anderson, supra, at
575 (the parties “have already been forced to concentrate
their energies and resources on persuading the trial judge
that their account of the facts is the correct one; requiring
them to persuade three more judges at the appellate level
is requiring too much”); Brief for Peter S. Menell et al. as
Amici Curiae 5 (Federal Circuit overturns district court
claim construction at unusually high rate).
   Finally, the Circuit feared that “clear error” review
would bring about less uniformity. Lighting Ballast,
supra, at 1280. Neither the Circuit nor Sandoz, however,
has shown that (or explained why) divergent claim con­
struction stemming from divergent findings of fact (on
subsidiary matters) should occur more than occasionally.
After all, the Federal Circuit will continue to review de
novo the district court’s ultimate interpretation of the
patent claims. And the attorneys will no doubt bring cases
construing the same claim to the attention of the trial
judge; those prior cases will sometimes be binding because
of issue preclusion, see Markman, 517 U. S., at 391, and
sometimes will serve as persuasive authority. Moreover,
10   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

it is always possible to consolidate for discovery different
cases that involve construction of the same claims. And,
as we said in Markman, subsidiary factfinding is unlikely
to loom large in the universe of litigated claim construc­
tion. Id., at 389–390.
                             C
  The dissent argues that claim construction does not
involve any “factfinding,” or, if it does, claim construction
factfinding is akin to the factfinding that underlies our
interpretation of statutes. Post, at 1, 5–7 (opinion of
THOMAS, J.). Its first, broader contention runs contrary to
our recognition in Markman that claim construction has
“evidentiary underpinnings” and that courts construing
patent claims must sometimes make “credibility judg­
ments” about witnesses. 517 U. S., at 389–390. Indeed, as
discussed in Part III, infra, this case provides a perfect
example of the factfinding that sometimes underlies claim
construction: The parties here presented the District
Court with competing fact-related claims by different
experts, and the District Court resolved the issues of fact
that divided those experts.
  The dissent’s contention also runs contrary to Sandoz’s
concession at oral argument that claim construction will
sometimes require subsidiary factfinding. Tr. of Oral Arg.
33–34, 38–40. It is in tension with our interpretation of
related areas of patent law, such as the interpretation of
“obviousness,” which we have said involves subsidiary
factfinding subject to Rule 52(a)’s clear error review. See
Dennison, 475 U. S., at 811. And it fights the question
presented in this case, which assumes the existence of
such factfinding. See Pet. for Cert. i (whether “a district
court’s factual finding in support of its construction of a
patent claim term may be reviewed de novo, . . . or only
for clear error”).
  Neither do we find factfinding in this context sufficiently
                 Cite as: 574 U. S. ____ (2015)          11

                     Opinion of the Court

similar to the factfinding that underlies statutory inter­
pretation. Statutes, in general, address themselves to the
general public; patent claims concern a small portion of
that public. Statutes typically (though not always) rest
upon congressional consideration of general facts related
to a reasonably broad set of social circumstances; patents
typically (though not always) rest upon consideration by a
few private parties, experts, and administrators of more
narrowly circumscribed facts related to specific technical
matters. The public, and often an adversarial public,
typically considers and discusses the relevant general
facts before Congress enacts a statute; only private par­
ties, experts, and administrators likely consider the rele­
vant technical facts before the award of a patent. Given
these differences, it is not surprising that this Court has
never previously compared patent claim construction in
any here relevant way to statutory construction. As dis­
cussed supra, at 5, however, the Court has repeatedly
compared patent claim construction to the construction of
other written instruments such as deeds and contracts.
See, e.g., Markman, supra, at 384, 386, 388, 389; Motion
Picture Patent Co., 243 U. S., at 510; Goodyear, 102 U. S.,
at 227.
                             D
  Now that we have set forth why the Federal Circuit
must apply clear error review when reviewing subsidiary
factfinding in patent claim construction, it is necessary to
explain how the rule must be applied in that context. We
recognize that a district court’s construction of a patent
claim, like a district court’s interpretation of a written
instrument, often requires the judge only to examine and
to construe the document’s words without requiring the
judge to resolve any underlying factual disputes. As all
parties agree, when the district court reviews only evi­
dence intrinsic to the patent (the patent claims and speci­
12   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

fications, along with the patent’s prosecution history), the
judge’s determination will amount solely to a determina­
tion of law, and the Court of Appeals will review that
construction de novo. See Brief for Petitioners 27, Re-
ply Brief 16; Brief for Respondents 43; see also Brief for
United States as Amicus Curiae 12–13.
    In some cases, however, the district court will need to
look beyond the patent’s intrinsic evidence and to consult
extrinsic evidence in order to understand, for example, the
background science or the meaning of a term in the rele­
vant art during the relevant time period. See, e.g., Sey-
mour v. Osborne, 11 Wall. 516, 546 (1871) (a patent may
be “so interspersed with technical terms and terms of art
that the testimony of scientific witnesses is indispensable
to a correct understanding of its meaning”). In cases
where those subsidiary facts are in dispute, courts will
need to make subsidiary factual findings about that ex­
trinsic evidence. These are the “evidentiary underpin­
nings” of claim construction that we discussed in Mark-
man, and this subsidiary factfinding must be reviewed for
clear error on appeal.
    For example, if a district court resolves a dispute be­
tween experts and makes a factual finding that, in gen­
eral, a certain term of art had a particular meaning to a
person of ordinary skill in the art at the time of the inven­
tion, the district court must then conduct a legal analysis:
whether a skilled artisan would ascribe that same mean­
ing to that term in the context of the specific patent claim
under review. That is because “[e]xperts may be examined
to explain terms of art, and the state of the art, at any
given time,” but they cannot be used to prove “the proper
or legal construction of any instrument of writing.”
Winans v. New York & Erie R. Co., 21 How. 88, 100–101
(1859); see also Markman, supra, at 388 (“ ‘Where tech­
nical terms are used, or where the qualities of substances
. . . or any similar data necessary to the comprehension of
                 Cite as: 574 U. S. ____ (2015)           13

                     Opinion of the Court

the language of the patent are unknown to the judge, the
testimony of witnesses may be received upon these sub­
jects, and any other means of information be employed.
But in the actual interpretation of the patent the court
proceeds upon its own responsibility, as an arbiter of the
law, giving to the patent its true and final character and
force’ ” (quoting 2 W. Robinson, Law of Patents §732, pp.
482–483 (1890); emphasis in original)).
  Accordingly, the question we have answered here con­
cerns review of the district court’s resolution of a subsidi­
ary factual dispute that helps that court determine the
proper interpretation of the written patent claim. The
district judge, after deciding the factual dispute, will then
interpret the patent claim in light of the facts as he has
found them. This ultimate interpretation is a legal con­
clusion. The appellate court can still review the district
court’s ultimate construction of the claim de novo. But, to
overturn the judge’s resolution of an underlying factual
dispute, the Court of Appeals must find that the judge, in
respect to those factual findings, has made a clear error.
Fed. Rule Civ. Proc. 52(a)(6).
  In some instances, a factual finding will play only a
small role in a judge’s ultimate legal conclusion about the
meaning of the patent term. But in some instances, a
factual finding may be close to dispositive of the ultimate
legal question of the proper meaning of the term in the
context of the patent. Nonetheless, the ultimate question
of construction will remain a legal question. Simply be­
cause a factual finding may be nearly dispositive does not
render the subsidiary question a legal one. “[A]n issue
does not lose its factual character merely because its
resolution is dispositive of the ultimate” legal question.
Miller v. Fenton, 474 U. S. 104, 113 (1985). It is analogous
to a judge (sitting without a jury) deciding whether a
defendant gave a confession voluntarily. The answer to
the legal question about the voluntariness of the confes­
14   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     Opinion of the Court

sion may turn upon the answer to a subsidiary factual
question, say “whether in fact the police engaged in the
intimidation tactics alleged by the defendant.” Id., at 112.
An appellate court will review the trial judge’s factual
determination about the alleged intimidation deferentially
(though, after reviewing the factual findings, it will review
a judge’s ultimate determination of voluntariness de novo).
See id., at 112–118. An appellate court similarly should
review for clear error those factual findings that underlie
a district court’s claim construction.
                             III
   We can illustrate our holding by considering an instance
in which Teva, with the support of the Solicitor General,
argues that the Federal Circuit wrongly reviewed the
District Court’s factual finding de novo. See Brief for
Petitioners 54–56; Brief for United States as Amicus
Curiae 31–32. Recall that Teva’s patent claim specifies an
active ingredient with a “molecular weight of about 5 to 9
kilodaltons.” Recall Sandoz’s basic argument, namely that
the term “molecular weight” is indefinite or ambiguous.
The term might refer to the weight of the most numerous
molecule, it might refer to weight as calculated by the
average weight of all molecules, or it might refer to weight
as calculated by an average in which heavier molecules
count for more. The claim, Sandoz argues, does not tell us
which way we should calculate weight. See Part I, supra.
   To illustrate, imagine we have a sample of copolymer-1
(the active ingredient) made up of 10 molecules: 4 weigh 6
kilodaltons each, 3 weigh 8 kilodaltons each, and 3 weigh
9 kilodaltons each. Using the first method of calculation,
the “molecular weight” would be 6 kilodaltons, the weight
of the most prevalent molecule. Using the second method,
the molecular weight would be 7.5 (total weight, 75, di-
vided by the number of molecules, 10). Using the third
method, the molecular weight would be more than 8, depend-
                 Cite as: 574 U. S. ____ (2015)          15

                     Opinion of the Court

ing upon how much extra weight we gave to the heavier
molecules.
   Teva argued in the District Court that the term “molec­
ular weight” in the patent meant molecular weight calcu­
lated in the first way (the weight of the most prevalent
molecule, or peak average molecular weight). Sandoz,
however, argued that figure 1 of the patent showed that
Teva could not be right. 810 F. Supp. 2d, at 590. (We
have set forth figure 1 in the Appendix, infra). That fig­
ure, said Sandoz, helped to show that the patent term did
not refer to the first method of calculation. Figure 1 shows
how the weights of a sample’s molecules were distributed
in three different samples. The curves indicate the num­
ber of molecules of each weight that were present in each
of the three. For example, the figure’s legend says that
the first sample’s “molecular weight” is 7.7. According to
Teva, that should mean that molecules weighing 7.7 kilo­
daltons were the most prevalent molecules in the sample.
But, look at the curve, said Sandoz. It shows that the
most prevalent molecule weighed, not 7.7 kilodaltons, but
slightly less than 7.7 (about 6.8) kilodaltons. See App.
138a–139a. After all, the peak of the first molecular
weight distribution curve (the solid curve in the figure) is
not at precisely 7.7 kilodaltons, but at a point just before
7.7. Thus, argued Sandoz, the figure shows that the pa­
tent claim term “molecular weight” did not mean molecu­
lar weight calculated by the first method. It must mean
something else. It is indefinite. 810 F. Supp. 2d, at 590.
   The District Court did not accept Sandoz’s argument.
Teva’s expert testified that a skilled artisan would under­
stand that converting data from a chromatogram to mo­
lecular weight distribution curves like those in figure 1
would cause the peak on each curve to shift slightly; this
could explain the difference between the value indicated
by the peak of the curve (about 6.8) and the value in the
figure’s legend (7.7). App. 138a–139a. Sandoz’s expert
16   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                      Opinion of the Court

testified that no such shift would occur. App. 375a–376a.
The District Court credited Teva’s expert’s account, thereby
rejecting Sandoz’s expert’s explanation. 810 F. Supp. 2d,
at 589; Brief for Respondents 61. The District Court’s
finding about this matter was a factual finding—about
how a skilled artisan would understand the way in which
a curve created from chromatogram data reflects molecu­
lar weights. Based on that factual finding, the District
Court reached the legal conclusion that figure 1 did not
undermine Teva’s argument that molecular weight re­
ferred to the first method of calculation (peak average
molecular weight). 810 F. Supp. 2d, at 590–591.
   When the Federal Circuit reviewed the District Court’s
decision, it recognized that the peak of the curve did not
match the 7.7 kilodaltons listed in the legend of figure 1.
723 F. 3d, at 1369. But the Federal Circuit did not accept
Teva’s expert’s explanation as to how a skilled artisan
would expect the peaks of the curves to shift. And it failed
to accept that explanation without finding that the Dis­
trict Court’s contrary determination was “clearly errone­
ous.” See ibid. The Federal Circuit should have accepted
the District Court’s finding unless it was “clearly errone­
ous.” Our holding today makes clear that, in failing to do
so, the Federal Circuit was wrong.
   Teva claims that there are two additional instances in
which the Federal Circuit rejected the District Court’s
factual findings without concluding that they were clearly
erroneous. We leave these matters for the Federal Circuit
to consider on remand in light of today’s opinion.
   We vacate the Federal Circuit’s judgment, and we re­
mand the case for further proceedings consistent with this
opinion.
                                             It is so ordered.
              Cite as: 574 U. S. ____ (2015) 
               17

                 Opinion
            Appendix      of the of
                     to opinion  Court
                                    the Court


                     APPENDIX





FIG. 1 (with minor additions to emphasize that the peak of
 the solid curve does not correspond precisely to 7.7kDa)
                     Cite as: 574 U. S. ____ (2015)                    1

                         THOMAS, J., dissenting

SUPREME COURT OF THE UNITED STATES
                              _________________

                              No. 13–854
                              _________________


      TEVA PHARMACEUTICALS USA, INC., ET AL., 

         PETITIONERS v. SANDOZ, INC., ET AL. 

 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

           APPEALS FOR THE FEDERAL CIRCUIT

                          [January 20, 2015]


   JUSTICE THOMAS, with whom JUSTICE ALITO joins,
dissenting.
   I agree with the Court’s conclusion that there is no
special exception to Federal Rule of Civil Procedure
52(a)(6) for claim construction. But that is not the ques­
tion in this case. Because Rule 52(a)(6) provides for clear
error review only of “findings of fact” and “does not apply
to conclusions of law,” Pullman-Standard v. Swint, 456
U. S. 273, 287 (1982), the question here is whether claim
construction involves findings of fact.1 Because it does
not, Rule 52(a)(6) does not apply, and the Court of Appeals
properly applied a de novo standard of review.
                             I
  In reaching the contrary conclusion, the majority fails to
——————
  1 The majority argues that we are bound by petitioners’ phrasing of
the question presented and by respondents’ concession at oral argu­
ment that claim construction “will sometimes require subsidiary
factfinding.” Ante, at 10–11. But the parties’ stipulations that claim
construction involves subsidiary factual determinations, with which I
do not quarrel, do not settle the question whether those determinations
are “findings of fact” within the meaning of Rule 52(a)(6). And to the
extent that the majority premises its holding on what it sees as stipula­
tions that these determinations are “findings of fact” for purposes of
Rule 52(a)(6), then its holding applies only to the present dispute, and
other parties remain free to contest this premise in the future.
2    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                    THOMAS, J., dissenting

engage the “vexing . . . distinction between questions of
fact and questions of law.” Id., at 288. Unfortunately,
“Rule 52(a) does not furnish particular guidance with
respect to distinguishing law from fact,” and we have
found it difficult to discern “any other rule or principle
that will unerringly” differentiate the two. Ibid. That
inquiry is thus not as simple as pointing out the undeni-
able “evidentiary underpinnings” of claim construction.
Ante, at 10–11.
  Instead, we must consider how “findings of fact” and
“conclusions of law” were understood at the time Rule 52
was adopted. Cf. Tome v. United States, 513 U. S. 150,
168 (1995) (SCALIA, J., concurring in part and concurring
in judgment) (noting that, because the federal rules have
their background in common-law principles, “the body of
common law knowledge must be a source of guidance in
our interpretation of the Rules” (internal quotation marks
omitted)). Unfortunately, the pre-1937 evidence of this
Court’s treatment of evidentiary determinations underly­
ing claim construction is inconclusive. In several deci­
sions, the Court considered extrinsic evidence related to
claim construction with no apparent deference to the
District Courts’ findings based on that evidence. Coupe v.
Royer, 155 U. S. 565, 576 (1895); Loom Co. v. Higgins, 105
U. S. 580, 584–587 (1882); Tilghman v. Proctor, 102 U. S.
707, 729–731 (1881); Winans v. Denmead, 15 How. 330,
339 (1854). None of those decisions, however, expressly
turned on a disagreement over a subsidiary evidentiary
determination.
  Absent specific evidence of the treatment of a particular
issue at the time Rule 52 was adopted, we have drawn
analogies to the treatment of other issues under Rule
52(a)(6). See, e.g., Pullman, supra, at 288. In general, we
have treated district-court determinations as “analytically
more akin to a fact” the more they pertain to a simple
historical fact of the case, and as “analytically more akin
                  Cite as: 574 U. S. ____ (2015)            3

                     THOMAS, J., dissenting

to . . . a legal conclusion” the more they define rules appli­
cable beyond the parties’ dispute. Miller v. Fenton, 474
U. S. 104, 116 (1985); see also Bose Corp. v. Consumers
Union of United States, Inc., 466 U. S. 485 (1984); Baum-
gartner v. United States, 322 U. S. 665, 671 (1944). Under
this approach, determinations underlying claim construc­
tion fall on the law side of the dividing line.
                               A
   Patents are written instruments, so other written in­
struments supply the logical analogy. See Markman v.
Westview Instruments, Inc., 517 U. S. 370, 381 (1996).
And as the majority recognizes, the construction of written
instruments is generally a question of law. See ante, at 5.
But in certain contexts, a court construing a written in­
strument makes subsidiary determinations that the law
treats as findings of fact.
   The classic case of a written instrument whose construc­
tion does not involve subsidiary findings of fact is a stat­
ute. Our treatment of subsidiary evidentiary findings
underlying statutory construction as conclusions of law
makes sense for two reasons.
   First, although statutory construction may demand
some inquiry into legislative “intent,” that inquiry is an-
alytically legal: The meaning of a statute does not turn
on what an individual lawmaker intended as a matter of
fact, but only on what intent has been enacted into law
through the constitutionally defined channels of bicamer­
alism and presentment. See Wyeth v. Levine, 555 U. S.
555, 587 (2009) (THOMAS, J., concurring in judgment).
This remains so even if deciding what passed through
those channels requires a court to determine a “fact” of
historical understanding through an examination of ex­
trinsic evidence. See, e.g., Sosa v. Alvarez-Machain, 542
U. S. 692, 714–715 (2004) (examining the historical under­
standing of the term “law of nations” when the Alien Tort
4    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     THOMAS, J., dissenting

Statute was enacted); see also, e.g., McIntyre v. Ohio
Elections Comm’n, 514 U. S. 334, 359–366 (1995)
(THOMAS, J., concurring in judgment) (construing a consti­
tutional provision by asking how the words were originally
understood and marshaling evidence of that understand­
ing). The Court has given no hint that this practice
changes when the statute it construes is a land patent—
that is, a public land grant. See Leo Sheep Co. v. United
States, 440 U. S. 668, 669 (1979) (making detailed histori­
cal findings in the course of construing a land grant be­
cause “ ‘courts, in construing a statute, may with propriety
recur to the history of the times when it was passed . . . in
order to ascertain the reason as well as the meaning of
particular provisions in it’ ”); see also Marvin M. Brandt
Revocable Trust v. United States, 572 U. S. ___, ___ (2014)
(slip op., at 10) (looking to the historical background
against which a land grant was passed to confirm its
interpretation).
   Second, statutes govern the rights and duties of the
public as a whole, so subsidiary evidentiary findings shape
legal rules that apply far beyond the boundaries of the
dispute involved. Our rules of construction for legislative
acts have long been consciously shaped by the public’s
stake in those acts. See, e.g., The Binghamton Bridge, 3
Wall. 51, 75 (1866) (describing a rule of construction bor­
rowed from English common law and reflected in the
decisions of the several States).
   The construction of contracts and deeds, by contrast,
sometimes involves subsidiary findings of fact.          Our
treatment of subsidiary evidentiary findings as findings of
fact in this context makes sense because, in construing
contracts and deeds, “the avowed purpose and primary
function of the court is to ascertain the intention of the
parties.” 11 R. Lord, Williston on Contracts §30:2, pp. 17–
18 (4th ed. 2012) (Williston); see also Reed v. Proprietors of
Locks and Canals on Merrimac River, 8 How. 274, 288–
                  Cite as: 574 U. S. ____ (2015)             5

                     THOMAS, J., dissenting

289 (1850). Sometimes that intention is clearly “set forth
in the express language of the contract,” 11 Williston
§31:1, at 341–342, so no subsidiary findings of fact are
necessary to its construction, id., §30:1. But when ambi­
guities require a court to look beyond the express lan­
guage, its search for intent becomes factual in nature.
That search focuses on “real intention[s]”—embodied in an
actual meeting of minds or an actual conveyance of a
physical parcel of land—that have an existence outside the
written instrument and that the instrument merely rec­
ords. See William & James Brown & Co. v. McGran, 14
Pet. 479, 493 (1840) (Story, J.); Reed, supra, at 289. See
generally Union Pacific R. Co. v. United States, 10 Ct. Cl.
548, 577–578 (1874) (declining to interpret a contract-like
statute according to contract rules because “[a]ll the terms
of the compact are dictated and accepted by one side, and
the only intent which judicial construction can make
certain is the intent of the legislative power”), cited in 3 N.
Singer, Sutherland on Statutory Construction §63:1, p.
405, n. 6 (7th ed. 2008).
   Of course, not all subsidiary inquiries that a court
makes in the course of construing contracts amount to
findings of fact. For example, when a court searches for
the meaning that a hypothetical person “conversant with
the subject-matter with which the contract is dealing”
would give to the words of the contract, its conclusion
often remains one of law. Silver King Coalition Mines Co.
of Nevada v. Silver King Consol. Mining Co. of Utah, 204
F. 166 (CA8 1913), cited in Advisory Committee’s 1937
Notes on Fed. Rule Civ. Proc. 52, 28 U. S. C. App., p. 686.
   The question we must ask, then, is whether the subsidi­
ary findings underlying claim construction more closely
resemble the subsidiary findings underlying the construc­
tion of statutes or those underlying the construction of
contracts and deeds that are treated as findings of fact.
This, in turn, depends on whether patent claims are more
6    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                    THOMAS, J., dissenting

like statutes or more like contracts and deeds.
                               B
   A patent, generally speaking, is “an official document
reflecting a grant by a sovereign that is made public, or
‘patent.’ ” Marvin M. Brandt Revocable Trust, supra, at ___
(slip op., at 5). Invention patents originated not as private
property rights, but as royal prerogatives. See 4 W.
Holdsworth, A History of English Law 350–351 (1924).
They could be issued and revoked only by the Crown,
which sometimes used the patent to delegate governmen­
tal power to regulate an industry. Id., at 344–347. Pro­
voked by the Crown’s use of these so-called “monopoly
patents” to promote private economic interests over inno­
vation and beneficial commerce, Parliament enacted the
Statute of Monopolies in 1624. Id., at 353. But even
under the regime that Parliament put in place, patents
remained sovereign grants, issued, enforced, and revoked
by the Privy Council. Lemley, Why Do Juries Decide if
Patents are Valid? 99 Va. L. Rev. 1673, 1681 (2013).
   The Framers adopted a similar scheme. Article I of the
U. S. Constitution vests the patent power in Congress,
authorizing it “[t]o promote the Progress of Science and
useful Arts, by securing for limited Times to Authors and
Inventors the exclusive Right to their respective Writings
and Discoveries.” U. S. Const. Art. I, §8, cl. 8. Although
Congress could issue such patents as special statutes, see,
e.g., Bloomer v. McQuewan, 14 How. 539, 549–550 (1853),
it has mostly acted by authorizing the Executive Branch to
issue patents when certain statutory requirements are
met. See 35 U. S. C. §151; see also Act of July 8, 1870,
§31, 16 Stat. 202; Act of July 4, 1836, §7, 5 Stat. 119; Act
of Apr. 10, 1790, ch. 7, §1, 1 Stat. 109–110.
   Like the royal prerogatives that were their historical
antecedents, patents have a regulatory effect: They “re­
strain others from manufacturing, using or selling that
                 Cite as: 574 U. S. ____ (2015)           7

                    THOMAS, J., dissenting

which [the patent holder] has invented” for a specified
period of time. Motion Picture Patents Co. v. Universal
Film Mfg. Co., 243 U. S. 502, 510 (1917) (emphasis added).
And because the regulatory scope of a patent is deter­
mined by the claims in the patent, the subsidiary findings
that a court makes during claim construction contribute to
rules that limit conduct by the public at large.
  Because they are governmental dispositions and provide
rules that bind the public at large, patent claims resemble
statutes. The scope of a patent holder’s monopoly right is
defined by claims legally actualized through the proce­
dures established by Congress pursuant to its patent
power. Thus, a patent holder’s actual intentions have
effect only to the extent that they are expressed in the
public record. See Keystone Bridge Co. v. Phoenix Iron
Co., 95 U. S. 274, 279 (1877); see also Goodyear Dental
Vulcanite Co. v. Davis, 102 U. S. 222, 227 (1880) (examin­
ing “the avowed understanding of the patentee,” but dis­
claiming any holding that such understanding “c[ould] be
allowed to enlarge, diminish, or vary the language of a
patent afterwards issued”).
  Moreover, because the ultimate meaning of a patent
claim, like the ultimate meaning of a statute, binds the
public at large, it should not depend on the specific evi­
dence presented in a particular infringement case. Al­
though the party presentations shape even statutory con-
struction, de novo review on appeal helps to ensure that
the construction is not skewed by the specific evidence
presented in a given case.
                            C
  For purposes of construction, contracts and deeds are
less natural analogies for patents. In particular, patents
lack the characteristics of those instruments that have
justified departing from the usual practice of treating
document construction as a wholly legal inquiry, not sub­
8    TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     THOMAS, J., dissenting

ject to subsidiary findings of fact.
  To be sure, we have occasionally characterized a patent
as “a carefully crafted bargain” between the inventor and
the public. Pfaff v. Wells Electronics, Inc., 525 U. S. 55, 63
(1998); see also Kendall v. Winsor, 21 How. 322, 327–328
(1859); Grant v. Raymond, 6 Pet. 218, 242 (1832). But, as
our decisions have also recognized, the patent is perhaps
better characterized as a reward for feats already accom­
plished—that is, innovation and public disclosure—than
as a mutual exchange of executory promises. See, e.g.,
Motion Picture Patents Co., supra, at 513; Seymour v.
Osborne, 11 Wall. 516, 533–534 (1871); Grant, supra, at
242; see also Markman v. Westview Instruments, Inc., 52
F. 3d 967, 985, n. 14 (CA Fed. 1995), aff ’d 517 U. S. 370
(1996) (distinguishing patents from contracts). In grant­
ing a patent, the Government is acting not as a party to a
bilateral contract binding upon itself alone, but instead as
a sovereign bestowing upon the inventor a right to exclude
the public at large from the invention marked out by his
claims.
  In this sense, patents are more closely analogous to
deeds, Motion Picture Patents Co., supra, at 510 (collecting
cases), because they share the common characteristic of
describing rights that the owner holds against the world.
See Bonito Boats, Inc. v. Thunder Craft Boats, Inc., 489
U. S. 141, 162 (1989). But in the context of land patents,
we have been unwilling to interpret sovereign dispositions
in the same way we interpret analogous private convey­
ances. See, e.g., Leo Sheep Co., 440 U. S., at 680–682;
Missouri, K. & T. R. Co. v. Kansas Pacific R. Co., 97 U. S.
491, 497 (1878); Leavenworth, L. & G. R. Co. v. United
States, 92 U. S. 733, 740–741 (1876); see also Marvin M.
Brandt Revocable Trust, supra (interpreting a land grant
as a statute rather than as a deed). We should not blithely
extend the rules governing the construction of deeds to
                      Cite as: 574 U. S. ____ (2015)                     9

                         THOMAS, J., dissenting

their even more distant cousins, invention patents.2
  Bearing these differences in mind, the subsidiary facts
relevant to the construction of patents, on the one hand,
and contracts and deeds, on the other, differ substantially.
As explained above, we have justified treating subsidiary
determinations about the actual intentions of parties to
contracts and deeds as findings of fact. But the subsidiary
determinations about patent claims that the majority
identifies as factual do not concern historical facts, such as
what the parties agreed to do or how a given parcel of land
——————
   2 The Anglo-American legal tradition has long distinguished between

“core” private rights—including the traditional property rights repre­
sented by deeds—and other types of rights. Nelson, Adjudication in the
Political Branches, 107 Colum. L. Rev. 559, 567 (2007) (Nelson). These
other rights fall into two categories: “ ‘public rights belonging to the
people at large,’ ” and “privileges” or “franchises,” “which public author­
ities ha[ve] created purely for reasons of public policy and which ha[ve]
no counterpart in the Lockean state of nature.” Id., at 566–567 Not­
withstanding a movement to recognize a “core” property right in inven­
tions, the English common law placed patents squarely in the final
category, as franchises that “depend upon express legislation,” and
“hath [their] essence by positive municipal law.” 7 W. Holdsworth, A
History of English Law 479, n. 7, 480, and n. 4, 497 (1926). The distinc­
tion between “core” private rights, on the one hand, and public rights
and government-created privileges, on the other, has traditionally had
significant implications for the way in which rights are adjudicated.
Nelson, supra. Thus, no matter how closely a franchise resembles some
“core” private right, it does not follow that it must be subject to the
same rules of judicial interpretation as its counterpart.
   Cases interpreting deeds and land patents exemplify this rule and
show why the majority’s assertion that patents affect fewer people than
statutes, in addition to being a dubious overgeneralization, is not a
material distinction. Land patents are more like deeds than statutes in
the sense that their effects are more localized, yet the judicial power
approaches them differently because they dispose of public rights held
by the government on behalf of the people, Nelson 566. See also The
Binghamton Bridge, 3 Wall. 51, 75 (1866) (interpreting a state grant of
a corporate charter as a “contract” but subject to the special common-
law rule that all ambiguities must be construed in favor of the State
because “in grants by the public nothing passes by implication”).
10   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     THOMAS, J., dissenting

is situated. See William & James Brown & Co., 14 Pet., at
493; Reed, 8 How., at 289.
   For example, the “fact” of how a skilled artisan would
understand a given term or phrase at a particular point in
history is a legal fiction; it has no existence independent of
the claim construction process. There is no actual “skilled
artisan” who, at the moment the application was filed,
formed an understanding of the terms of the claim—an
understanding that an omniscient factfinder could ascer­
tain. Neither is the skilled artisan’s understanding a
proxy for some external fact that, could the court know it,
would supply the meaning of a patent claim. Whatever
the scope of the inventor’s right under the patent before
the introduction of claims, the law has limited that right
to the claims as written in the patent. See Markman,
supra, at 379. Our decision in Markman rested in part on
this characteristic of claim construction, distinguishing it
from other patent determinations that must go to a jury
because they require the factfinder to inspect “ ‘an embod­
ied conception outside of the patent itself ’ ” or things
“ ‘which have their existence in pais.’ ” 517 U. S., at 385–
386 (distinguishing Bischoff v. Wethered, 9 Wall. 812
(1870)).
   Because the skilled artisan inquiry in claim construction
more closely resembles determinations categorized as
“conclusions of law” than determinations categorized as
“findings of fact,” I would hold that it falls outside the
scope of Rule 52(a)(6) and is subject to de novo review.
                            II

                            A

  The majority makes little effort to justify its assertion
that the subsidiary determinations a district court makes
in the course of claim construction are findings of fact.
And the few analogies that it attempts to draw either lack
support or prove too much.
                 Cite as: 574 U. S. ____ (2015)           11

                    THOMAS, J., dissenting

   For example, relying on Great Northern R. Co. v. Mer-
chants Elevator Co., 259 U. S. 285, 292 (1922), the major-
ity compares the search for the meaning of “ ‘technical
words or phrases not commonly understood’ ” in claim
construction to “questions of fact” about the scope of a
railway tariff. See ante, at 6. It is true that, in Great
Northern, the Court referred to questions of fact arising in
the context of contract construction, which, it pointed out,
must go to a jury. 259 U. S., at 292–293. But the Court’s
conclusion that similar questions must be settled by the
Interstate Commerce Commission (ICC) when they relate
to the interpretation of a railway tariff merely proves the
point that the allocation of a technical usage inquiry de­
pends upon the legal instrument that the court is constru­
ing. In that case, the Court was faced with a tariff filed
with, and administered by, the ICC. And it was not con­
cerned with allocating evidentiary determinations be­
tween trial and appellate courts, but with allocating them
between an agency and the judiciary. Id., at 289. So
understood, the distinction the Court drew pertains more
to an emerging rule of administrative deference than to a
definitive classification of judicial determinations.
   Further reinforcing the point that the nature of the legal
instrument dictates our treatment of subsidiary findings is
that, although terms in statutes and regulations frequently
have technical meanings unknown outside the special-
ized community they are meant to regulate, we treat the
inquiry into those meanings as involving only conclusions
of law. See, e.g., Norfolk & Western R. Co. v. Hiles, 516
U. S. 400, 401–407, 413–414 (1996); Aluminum Co. of
America v. Central Lincoln Peoples’ Util. Dist., 467 U. S.
380, 390 (1984). The majority’s unexamined reliance on
technical usage could be read to cast doubt on this prac­
tice, as well as on our holding in Markman that claim
construction is exclusively for the court. If claim construc­
tion involves subsidiary questions of technical meaning or
12   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     THOMAS, J., dissenting

usage that are indistinguishable from those questions
submitted to the jury in the contract context, see 12 Wil­
liston §34:19, then one might wonder why such issues are
not submitted to the jury in the patent and statute con­
texts, too.
   The majority also analogizes to the obviousness inquiry
in patent law, which involves findings of fact subject to
Rule 52(a)(6). Ante, at 11 (citing Dennison Mfg. Co. v.
Panduit Corp., 475 U. S. 809, 811 (1986) (per curiam)).
But this analogy is even further off the mark because
obviousness turns on historical facts about the circum­
stances of the invention, rather than on the construction of
a written instrument. Id., at 810–811. Cf. Markman,
supra, at 386 (distinguishing the novelty inquiry from
claim construction on these grounds).
                              B
   Nor does the majority attempt to justify its holding by
reference to which “ ‘judicial actor is better positioned . . .
to decide the issue in question,’ ” Markman, supra, at
388—an inquiry that we have also treated as relevant to
the classification of fact versus law, Miller, 474 U. S., at
114. In resolving issues of judicial administration, we
have considered that federal appellate courts are “exposi­
tor[s] of law,” ibid., and have acknowledged that they are
better positioned than district courts to promote uniform-
ity, Markman, supra, at 390; see also Ornelas v. United
States, 517 U. S. 690, 697–698 (1996). We have recog­
nized, however, that trial courts have a special competence
in judging witness credibility and weighing the evidence,
Miller, supra, at 114, and have been cautious not to waste
judicial and party resources through needless relitigation,
see Anderson v. Bessemer City, 470 U. S. 564, 575 (1985).
   To the extent that the construction of a patent claim
turns on testimony of expert witnesses, especially live
testimony, there is no denying that it falls within the
                 Cite as: 574 U. S. ____ (2015)          13

                    THOMAS, J., dissenting

bounds of a district court’s special competence. But as we
recognized in Markman, and as the majority is careful to
reiterate today, “subsidiary factfinding is unlikely to loom
large in the universe of litigated claim construction.”
Ante, at 10. The majority’s reluctance to highlight “alloca­
tion,” Miller, supra at 113, is thus understandable. The
arguments favoring allocation to the district court, dimin­
ished by the majority’s own prediction, are outweighed by
the remaining rule-of-law and uniformity considerations
that factored into our allocation in Markman, 517 U. S., at
388–391.
                               1
   We have long been cautious not to allocate issues in a
way that would “strip a federal appellate court of its pri­
mary function as an expositor of law.” Miller, 474 U. S., at
114. Although we have recognized that “an issue does not
lose its factual character merely because its resolution is
dispositive of the ultimate” dispute, id., at 113, we have
been less inclined to defer to seemingly factual determina­
tions that play a dispositive role in the development of
legal rules. For example, we have sanctioned de novo
appellate review of the mixed determinations of “probable
cause” and “reasonable suspicion” on the ground that “the
legal rules . . . acquire content only through application.”
Ornelas, supra, 697; see also Miller, supra, at 116. Al-
though such determinations depend on the specific facts in
a case, their role in shaping rules of law demand a de novo
standard of review.
   As previously noted, patents are authoritative govern­
mental dispositions. Thus, when a judge construes a
patent, he is, in a very real sense, “say[ing] what the law
is,” Marbury v. Madison, 1 Cranch 137, 177 (1803), not
just for the parties to the dispute, but for the public at
large. It follows that, any time a district court’s claim
construction turns on subsidiary evidentiary disputes, the
14   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                     THOMAS, J., dissenting

majority’s rule will distort the appellate court’s construc­
tion of the law by requiring it to defer to subsidiary deter­
minations that are dispositive as to its meaning. Surely
the majority would not countenance such an abdication
of the appellate court’s role in the construction of statutes.
Yet the majority has not justified applying a different rule
to the construction of legislative acts that take the form of
a patent.
                              2
  The need for uniformity in claim construction also
weighs heavily in favor of de novo review of subsidiary
evidentiary determinations. Uniformity is a critical fea­
ture of our patent system because “ ‘[t]he limits of a patent
must be known for the protection of the patentee, the
encouragement of the inventive genius of others and the
assurance that the subject of the patent will be dedicated
ultimately to the public.’ ” Markman, 517 U. S., at 390. If
the boundaries of the patent right could shift from case to
case, then the result would be “a ‘zone of uncertainty
which enterprise and experimentation may enter only at
the risk of infringement.’ ” Ibid.; see also Festo Corp. v.
Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U. S. 722, 731
(2002). So damaging is this unpredictability that we
identified uniformity as an “independent” reason justify­
ing our allocation of claim construction to the court. See
Markman, supra, at 390.
  The majority attempts to downplay the effect its deci­
sion will have on uniformity by pointing out that “prior
cases [construing the same claim] will sometimes be bind­
ing because of issue preclusion, and sometimes will serve
as persuasive authority.” Ante, at 9–10 (citing Markman,
supra, at 391; citation omitted). But we have already
rejected the notion that issue preclusion adequately safe­
guards the uniformity that our patent system requires.
See Markman, supra, at 391.
                 Cite as: 574 U. S. ____ (2015)           15

                    THOMAS, J., dissenting

   Perhaps the majority is correct that “subsidiary factfind­
ing is unlikely to loom large in the universe of litigated
claim construction.” Ante, at 10. But I doubt it. If this
case proves anything, it is that the line between fact and
law is an uncertain one—made all the more uncertain by
the majority’s failure to identify sound principles for the
lines it draws. The majority’s rule provides litigants who
prevail in district court a significant opportunity and
incentive to take advantage of this uncertainty by arguing
on appeal that the district court’s claim construction in­
volved subsidiary findings of fact. At best, today’s holding
will spawn costly—and, if the majority is correct about the
frequency with which these evidentiary determinations
make a difference, meritless—collateral litigation over the
line between law and fact. We generally avoid any rule of
judicial administration that “results in a substantial
expenditure of scarce judicial resources on difficult ques­
tions that have no effect on the outcome of the case,” Pear-
son v. Callahan, 555 U. S. 223, 236–237 (2009), and there
is no reason to embrace one here. But I fear worse: that
today’s decision will result in fewer claim construction
decisions receiving precedential effect, thereby injecting
uncertainty into the world of invention and innovation.
   In short, the majority’s rule finds no support in either
the historical understanding of “findings of fact” or consid­
erations of policy that have served as our guide when we
have been confronted with a difficult question of fact-law
classification. I would not adopt it.
                             III
  The Court of Appeals reviewed de novo not only the
District Court’s claim construction, but also its holding
that the claims were sufficiently definite to satisfy 35
U. S. C. §112, ¶2 (2006 ed.). I would hold that the Court of
Appeals correctly treated the indefiniteness inquiry as a
question of law because it depends entirely on claim
16   TEVA PHARMACEUTICALS USA, INC. v. SANDOZ, INC.

                      THOMAS, J., dissenting

construction.
   “[A] patent is invalid for indefiniteness if its claims, read
in light of the specification delineating the patent, and the
prosecution history, fail to inform, with reasonable cer­
tainty, those skilled in the art about the scope of the in­
vention.” Nautilus, Inc. v. Biosig Instruments, Inc., 572
U. S. ___, ___ (2014) (slip op., at 1). This standard falls
somewhere between a notice requirement and a prohibi­
tion on ambiguity. See id., at ___ –___ (slip op., at 9–11).
Determining whether a claim is indefinite is thus akin to
other legal inquiries commonly performed in the course of
interpreting written instruments. See, e.g., Mayo Founda-
tion for Medical Ed. and Research v. United States, 562
U. S. 44, 52–53 (2011) (reviewing without deference the
district court’s determination that a statute is unambigu­
ous at step one of Chevron U. S. A. Inc. v. Natural Re-
sources Defense Council, Inc., 467 U. S. 837 (1984)); 11
Williston §30:5, at 75 (“The determination of whether a
contract is ambiguous is a question of law for the court”).
Thus, a holding that a patent satisfies the definiteness
requirement does not turn on “findings of fact” as that
term is used in Rule 52(a)(6), and the Court of Appeals
properly applied a de novo standard of review.
                      *     *     *
  Although it relied on expert testimony to understand
the science underlying petitioners’ claims, the District
Court made no “findings of fact” as that term is used in
Rule 52(a)(6). Thus, the Court of Appeals properly re­
viewed the District Court’s conclusions of law de novo. I
respectfully dissent.
