(Slip Opinion) OCTOBER TERM, 2013 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 

NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 

THE FEDERAL CIRCUIT 

No. 13–369. Argued April 28, 2014—Decided June 2, 2014 

The Patent Act requires that a patent specification “conclude with one 

or more claims particularly pointing out and distinctly claiming the 

subject matter which the applicant regards as [the] invention.” 35 

U. S. C. §112, ¶2. This case concerns the proper reading of the statute’s clarity and precision demand. 

Assigned to respondent Biosig Instruments, Inc., the patent in dispute (the ’753 patent) involves a heart-rate monitor used with exercise equipment. Prior heart-rate monitors, the patent asserts, were

often inaccurate in measuring the electrical signals accompanying

each heartbeat (electrocardiograph or ECG signals) because of the 

presence of other electrical signals (electromyogram or EMG signals),

generated by the user’s skeletal muscles, that can impede ECG signal

detection. The invention claims to improve on prior art by detecting

and processing ECG signals in a way that filters out the EMG interference. 

Claim 1 of the ’753 patent, which contains the limitations critical to

this dispute, refers to a “heart rate monitor for use by a user in association with exercise apparatus and/or exercise procedures.” The 

claim “comprise[s],” among other elements, a cylindrical bar fitted

with a display device; “electronic circuitry including a difference amplifier”; and, on each half of the cylindrical bar, a “live” electrode and 

a “common” electrode “mounted . . . in spaced relationship with each 

other.” 

Biosig filed this patent infringement suit, alleging that Nautilus,

Inc., without obtaining a license, sold exercise machines containing 

Biosig’s patented technology. The District Court, after conducting a

hearing to determine the proper construction of the patent’s claims,

granted Nautilus’ motion for summary judgment on the ground that 
 

 

 

2 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Syllabus 

the claim term “in spaced relationship with each other” failed §112, 

¶2’s definiteness requirement. The Federal Circuit reversed and remanded, concluding that a patent claim passes the §112, ¶2 threshold so long as the claim is “amenable to construction,” and the claim,

as construed, is not “insolubly ambiguous.” Under that standard, the 

court determined, the ’753 patent survived indefiniteness review. 

Held: 

1. A patent is invalid for indefiniteness if its claims, read in light of 

the patent’s specification and prosecution history, fail to inform, with 

reasonable certainty, those skilled in the art about the scope of the 

invention. The parties agree that definiteness is to be evaluated from 

the perspective of a person skilled in the relevant art, that claims are

to be read in light of the patent’s specification and prosecution history, and that definiteness is to be measured as of the time of the patent application. The parties disagree as to how much imprecision 

§112, ¶2 tolerates. 

Section 112’s definiteness requirement must take into account the 

inherent limitations of language. See Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U. S. 722, 731. On the one hand, some 

modicum of uncertainty is the “price of ensuring the appropriate incentives for innovation,” id., at 732; and patents are “not addressed to

lawyers, or even to the public generally,” but to those skilled in the

relevant art, Carnegie Steel Co. v. Cambria Iron Co., 185 U. S. 403, 

437. At the same time, a patent must be precise enough to afford

clear notice of what is claimed, thereby “ ‘appris[ing] the public of 

what is still open to them,’ ” Markman v. Westview Instruments, Inc., 

517 U. S. 370, 373, in a manner that avoids “[a] zone of uncertainty 

which enterprise and experimentation may enter only at the risk of 

infringement claims,” United Carbon Co. v. Binney & Smith Co., 317 

U. S. 228, 236. The standard adopted here mandates clarity, while 

recognizing that absolute precision is unattainable. It also accords 

with opinions of this Court stating that “the certainty which the law

requires in patents is not greater than is reasonable, having regard 

to their subject-matter.” Minerals Separation, Ltd. v. Hyde, 242 U. S. 

261, 270. Pp. 8–11. 

2. The Federal Circuit’s standard, which tolerates some ambiguous

claims but not others, does not satisfy the statute’s definiteness requirement. The Court of Appeals inquired whether the ’753 patent’s 

claims were “amenable to construction” or “insolubly ambiguous,” but

such formulations lack the precision §112, ¶2 demands. To tolerate 

imprecision just short of that rendering a claim “insolubly ambiguous” would diminish the definiteness requirement’s public-notice 

function and foster the innovation-discouraging “zone of uncertainty,” 

United Carbon, 317 U. S., at 236, against which this Court has 
 

Cite as: 572 U. S. ____ (2014) 3 

Syllabus 

warned. While some of the Federal Circuit’s fuller explications of the

term “insolubly ambiguous” may come closer to tracking the statutory prescription, this Court must ensure that the Federal Circuit’s test 

is at least “probative of the essential inquiry.” Warner-Jenkinson Co. 

v. Hilton Davis Chemical Co., 520 U. S. 17, 40. The expressions “insolubly ambiguous” and “amenable to construction,” which permeate

the Federal Circuit’s recent decisions concerning §112, ¶2, fall short 

in this regard and can leave courts and the patent bar at sea without

a reliable compass. Pp. 11–13.

3. This Court, as “a court of review, not of first view,” Cutter v. Wilkinson, 544 U. S. 709, 718, n. 7, follows its ordinary practice of remanding so that the Federal Circuit can reconsider, under the proper 

standard, whether the relevant claims in the ’753 patent are sufficiently definite, see, e.g., Johnson v. California, 543 U. S. 499, 515. 

Pp. 13–14. 

715 F. 3d 891, vacated and remanded. 

GINSBURG, J., delivered the opinion for a unanimous Court. 
 

 

_________________ 

_________________ 

 

Cite as: 572 U. S. ____ (2014) 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, Washington, 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. 13–369 

NAUTILUS, INC., PETITIONER v. BIOSIG 

INSTRUMENTS, INC.
 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 

APPEALS FOR THE FEDERAL CIRCUIT
 

[June 2, 2014]

 JUSTICE GINSBURG delivered the opinion of the Court. 

The Patent Act requires that a patent specification

“conclude with one or more claims particularly pointing 

out and distinctly claiming the subject matter which the 

applicant regards as [the] invention.” 35 U. S. C. §112, ¶2 

(2006 ed.) (emphasis added). This case, involving a heartrate monitor used with exercise equipment, concerns the

proper reading of the statute’s clarity and precision demand. According to the Federal Circuit, a patent claim 

passes the §112, ¶2 threshold so long as the claim is

“amenable to construction,” and the claim, as construed, is 

not “insolubly ambiguous.” 715 F. 3d 891, 898–899 (2013). 

We conclude that the Federal Circuit’s formulation, which 

tolerates some ambiguous claims but not others, does not 

satisfy the statute’s definiteness requirement. In place of 

the “insolubly ambiguous” standard, we hold that 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 certainty,

those skilled in the art about the scope of the invention. 

Expressing no opinion on the validity of the patent-in-suit, 
 

2 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

we remand, instructing the Federal Circuit to decide the 

case employing the standard we have prescribed. 

I 

Authorized by the Constitution “[t]o promote the Progress of Science and useful Arts, by securing for limited 

Times to . . . Inventors the exclusive Right to their . . .

Discoveries,” Art. I, §8, cl. 8, Congress has enacted patent

laws rewarding inventors with a limited monopoly. 

“Th[at] monopoly is a property right,” and “like any property right, its boundaries should be clear.” Festo Corp. v. 

Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U. S. 722, 730 

(2002). See also Markman v. Westview Instruments, Inc., 

517 U. S. 370, 373 (1996) (“It has long been understood 

that a patent must describe the exact scope of an invention and its manufacture . . . .”). Thus, when Congress 

enacted the first Patent Act in 1790, it directed that patent grantees file a written specification “containing a 

description . . . of the thing or things . . . invented or discovered,” which “shall be so particular” as to “distinguish

the invention or discovery from other things before known 

and used.” Act of Apr. 10, 1790, §2, 1 Stat. 110.

The patent laws have retained this requirement of 

definiteness even as the focus of patent construction has 

shifted. Under early patent practice in the United States,

we have recounted, it was the written specification that 

“represented the key to the patent.” Markman, 517 U. S., 

at 379. Eventually, however, patent applicants began to

set out the invention’s scope in a separate section known

as the “claim.” See generally 1 R. Moy, Walker on Patents

§4.2, pp. 4–17 to 4–20 (4th ed. 2012). The Patent Act of 

1870 expressly conditioned the receipt of a patent on the

inventor’s inclusion of one or more such claims, described 

with particularity and distinctness. See Act of July 8,

1870, §26, 16 Stat. 201 (to obtain a patent, the inventor 

must “particularly point out and distinctly claim the part, 
Cite as: 572 U. S. ____ (2014) 3 

Opinion of the Court 

improvement, or combination which [the inventor] claims

as his invention or discovery”).

The 1870 Act’s definiteness requirement survives today,

largely unaltered. Section 112 of the Patent Act of 1952, 

applicable to this case, requires the patent applicant to 

conclude the specification with “one or more claims particularly pointing out and distinctly claiming the subject

matter which the applicant regards as his invention.” 35 

U. S. C. §112, ¶2 (2006 ed.). A lack of definiteness renders 

invalid “the patent or any claim in suit.” §282, ¶2(3).1 

II
 

A 

The patent in dispute, U. S. Patent No. 5,337,753 (’753

patent), issued to Dr. Gregory Lekhtman in 1994 and 

assigned to respondent Biosig Instruments, Inc., concerns

a heart-rate monitor for use during exercise. Previous 

heart-rate monitors, the patent asserts, were often inaccurate in measuring the electrical signals accompanying

each heartbeat (electrocardiograph or ECG signals). The 

inaccuracy was caused by electrical signals of a different 

sort, known as electromyogram or EMG signals, generated 

by an exerciser’s skeletal muscles when, for example, she

moves her arm, or grips an exercise monitor with her

hand. These EMG signals can “mask” ECG signals and 

thereby impede their detection. App. 52, 147. 

—————— 

1 In the Leahy-Smith America Invents Act, Pub. L. 112–29, 125 Stat. 

284, enacted in 2011, Congress amended several parts of the Patent

Act. Those amendments modified §§112 and 282 in minor respects not

pertinent here. In any event, the amended versions of those provisions 

are inapplicable to patent applications filed before September 16, 2012,

and proceedings commenced before September 16, 2011. See §§4(e), 

15(c), 20(l), 125 Stat. 297, 328, 335, notes following 35 U. S. C. §§2, 111, 

119. Here, the application for the patent-in-suit was filed in 1992, and

the relevant court proceedings were initiated in 2010. Accordingly, this

opinion’s citations to the Patent Act refer to the 2006 edition of the

United States Code. 
 

 

4 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

Dr. Lekhtman’s invention claims to improve on prior art 

by eliminating that impediment. The invention focuses on 

a key difference between EMG and ECG waveforms: while 

ECG signals detected from a user’s left hand have a polarity opposite to that of the signals detected from her right

hand,2 EMG signals from each hand have the same polarity. The patented device works by measuring equalized 

EMG signals detected at each hand and then using circuitry to subtract the identical EMG signals from each

other, thus filtering out the EMG interference. 

As relevant here, the ’753 patent describes a heart-rate

monitor contained in a hollow cylindrical bar that a user 

grips with both hands, such that each hand comes into

contact with two electrodes, one “live” and one “common.” 

The device is illustrated in figure 1 of the patent, id., at 

41, reproduced in the Appendix to this opinion.

Claim 1 of the ’753 patent, which contains the limitations critical to this dispute, refers to a “heart rate monitor 

for use by a user in association with exercise apparatus 

and/or exercise procedures.” Id., at 61. The claim “comprise[s],” among other elements, an “elongate member” 

(cylindrical bar) with a display device; “electronic circuitry

including a difference amplifier”; and, on each half of the

cylindrical bar, a live electrode and a common electrode 

“mounted . . . in spaced relationship with each other.” 

Ibid.3 The claim sets forth additional elements, including 

that the cylindrical bar is to be held in such a way that 

each of the user’s hands “contact[s]” both electrodes on

each side of the bar. Id., at 62. Further, the EMG signals 

detected by the two electrode pairs are to be “of substan­

—————— 

2This difference in polarity occurs because the heart is not aligned 

vertically in relation to the center of the body; the organ tilts leftward

from apex to bottom. App. 213. 3As depicted in figure 1 of the patent, id., at 41, reproduced in the 

Appendix to this opinion, the live electrodes are identified by numbers 

9 and 13, and the common electrodes, by 11 and 15. 
Cite as: 572 U. S. ____ (2014) 5 

Opinion of the Court 

tially equal magnitude and phase” so that the difference

amplifier will “produce a substantially zero [EMG] signal” 

upon subtracting the signals from one another. Ibid. 

B 

The dispute between the parties arose in the 1990’s, 

when Biosig allegedly disclosed the patented technology to 

StairMaster Sports Medical Products, Inc. According to

Biosig, StairMaster, without ever obtaining a license, sold

exercise machines that included Biosig’s patented technology, and petitioner Nautilus, Inc., continued to do so after 

acquiring the StairMaster brand. In 2004, based on these 

allegations, Biosig brought a patent infringement suit 

against Nautilus in the U. S. District Court for the Southern District of New York. 

With Biosig’s lawsuit launched, Nautilus asked the U. S.

Patent and Trademark Office (PTO) to reexamine the ’753 

patent. The reexamination proceedings centered on

whether the patent was anticipated or rendered obvious 

by prior art—principally, a patent issued in 1984 to an

inventor named Fujisaki, which similarly disclosed a 

heart-rate monitor using two pairs of electrodes and a 

difference amplifier. Endeavoring to distinguish the ’753

patent from prior art, Biosig submitted a declaration from 

Dr. Lekhtman. The declaration attested, among other

things, that the ’753 patent sufficiently informed a person 

skilled in the art how to configure the detecting electrodes 

so as “to produce equal EMG [signals] from the left and 

right hands.” Id., at 160. Although the electrodes’ design 

variables—including spacing, shape, size, and material—

cannot be standardized across all exercise machines, Dr. 

Lekhtman explained, a skilled artisan could undertake a 

“trial and error” process of equalization. This would entail 

experimentation with different electrode configurations in 

order to optimize EMG signal cancellation. Id., at 155– 
 

6 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

156, 158.4 In 2010, the PTO issued a determination confirming the patentability of the ’753 patent’s claims.

Biosig thereafter reinstituted its infringement suit, 

which the parties had voluntarily dismissed without prejudice while PTO reexamination was underway. In 2011, 

the District Court conducted a hearing to determine the 

proper construction of the patent’s claims, see Markman v. 

Westview Instruments, Inc., 517 U. S. 370 (1996) (claim

construction is a matter of law reserved for court decision), 

including the claim term “in spaced relationship with each

other.” According to Biosig, that “spaced relationship”

referred to the distance between the live electrode and the 

common electrode in each electrode pair. Nautilus, seizing 

on Biosig’s submissions to the PTO during the reexamination, maintained that the “spaced relationship” must be a 

distance “greater than the width of each electrode.” App. 

245. The District Court ultimately construed the term to

mean “there is a defined relationship between the live 

electrode and the common electrode on one side of the 

cylindrical bar and the same or a different defined relationship between the live electrode and the common electrode on the other side of the cylindrical bar,” without any

reference to the electrodes’ width. App. to Pet. for Cert.

43a–44a. 

Nautilus moved for summary judgment, arguing that

the term “spaced relationship,” as construed, was indefinite under §112, ¶2. The District Court granted the motion. Those words, the District Court concluded, “did not 

tell [the court] or anyone what precisely the space should 

—————— 

4Dr. Lekhtman’s declaration also referred to an expert report prepared by Dr. Henrietta Galiana, Chair of the Department of Biomedical

Engineering at McGill University, for use in the infringement litigation. That report described how Dr. Galiana’s laboratory technician, 

equipped with a wooden dowel, wire, metal foil, glue, electrical tape, 

and the drawings from the ’753 patent, was able in two hours to build a

monitor that “worked just as described in the . . . patent.” Id., at 226. 
 

 

Cite as: 572 U. S. ____ (2014) 7 

Opinion of the Court 

be,” or even supply “any parameters” for determining the 

appropriate spacing. Id., at 72a. 

The Federal Circuit reversed and remanded. A claim is 

indefinite, the majority opinion stated, “only when it is

‘not amenable to construction’ or ‘insolubly ambiguous.’” 

715 F. 3d 891, 898 (2013) (quoting Datamize, LLC v. 

Plumtree Software, Inc., 417 F. 3d 1342, 1347 (CA Fed. 

2005)). Under that standard, the majority determined, the 

’753 patent survived indefiniteness review. Considering

first the “intrinsic evidence”—i.e., the claim language, the 

specification, and the prosecution history—the majority 

discerned “certain inherent parameters of the claimed 

apparatus, which to a skilled artisan may be sufficient to

understand the metes and bounds of ‘spaced relationship.’” 715 F. 3d, at 899. These sources of meaning, the

majority explained, make plain that the distance separating the live and common electrodes on each half of the bar 

“cannot be greater than the width of a user’s hands”; that 

is so “because claim 1 requires the live and common electrodes to independently detect electrical signals at two

distinct points of a hand.” Ibid. Furthermore, the majority noted, the intrinsic evidence teaches that this distance 

cannot be “infinitesimally small, effectively merging the 

live and common electrodes into a single electrode with

one detection point.” Ibid. The claim’s functional provisions, the majority went on to observe, shed additional 

light on the meaning of “spaced relationship.” Surveying

the record before the PTO on reexamination, the majority

concluded that a skilled artisan would know that she could 

attain the indicated functions of equalizing and removing

EMG signals by adjusting design variables, including 

spacing.

In a concurring opinion, Judge Schall reached the majority’s result employing “a more limited analysis.” Id., at 

905. Judge Schall accepted the majority’s recitation of the 

definiteness standard, under which claims amenable to 
 

 

 

 

8 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

construction are nonetheless indefinite when “the construction remains insolubly ambiguous.” Ibid. (internal

quotation marks omitted). The District Court’s construction of “spaced relationship,” Judge Schall maintained,

was sufficiently clear: the term means “there is a fixed

spatial relationship between the live electrode and the

common electrode” on each side of the cylindrical bar. 

Ibid. Judge Schall agreed with the majority that the

intrinsic evidence discloses inherent limits of that spacing.

But, unlike the majority, Judge Schall did not “presum[e]

a functional linkage between the ‘spaced relationship’ 

limitation and the removal of EMG signals.” Id., at 906. 

Other limitations of the claim, in his view, and not the 

“‘spaced relationship’ limitation itself,” “included a functional requirement to remove EMG signals.” Ibid. 

We granted certiorari, 571 U. S. ___ (2014), and now 

vacate and remand. 

III
 

A 

Although the parties here disagree on the dispositive 

question—does the ’753 patent withstand definiteness

scrutiny—they are in accord on several aspects of the 

§112, ¶2 inquiry. First, definiteness is to be evaluated 

from the perspective of someone skilled in the relevant art. 

See, e.g., General Elec. Co. v. Wabash Appliance Corp., 304 

U. S. 364, 371 (1938). See also §112, ¶1 (patent’s specification “shall contain a written description of the invention, 

and of the manner and process of making and using it, in

such full, clear, concise, and exact terms as to enable any 

person skilled in the art to which it pertains, or with which

it is most nearly connected, to make and use the same” 

(emphasis added)). Second, in assessing definiteness, 

claims are to be read in light of the patent’s specification 

and prosecution history. See, e.g., United States v. Adams, 

383 U. S. 39, 48–49 (1966) (specification); Festo Corp. v. 
 

Cite as: 572 U. S. ____ (2014) 9 

Opinion of the Court 

Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U. S. 722, 741 

(2002) (prosecution history). Third, “[d]efiniteness is

measured from the viewpoint of a person skilled in [the] 

art at the time the patent was filed.” Brief for Respondent 

55 (emphasis added). See generally E. Manzo, Patent

Claim Construction in the Federal Circuit §0.2, p. 9 (2014)

(“Patent claims . . . should be construed from an objective

perspective of a [skilled artisan], based on what the applicant actually claimed, disclosed, and stated during the 

application process.”).

The parties differ, however, in their articulations of just

how much imprecision §112, ¶2 tolerates. In Nautilus’ 

view, a patent is invalid when a claim is “ambiguous, such 

that readers could reasonably interpret the claim’s scope

differently.” Brief for Petitioner 37. Biosig and the Solicitor General would require only that the patent provide 

reasonable notice of the scope of the claimed invention. 

See Brief for Respondent 18; Brief for United States as 

Amicus Curiae 9–10. 

Section 112, we have said, entails a “delicate balance.” 

Festo, 535 U. S., at 731. On the one hand, the definiteness 

requirement must take into account the inherent limitations of language. See ibid. Some modicum of uncertainty, 

the Court has recognized, is the “price of ensuring the 

appropriate incentives for innovation.” Id., at 732. One 

must bear in mind, moreover, that patents are “not addressed to lawyers, or even to the public generally,” but 

rather to those skilled in the relevant art. Carnegie Steel 

Co. v. Cambria Iron Co., 185 U. S. 403, 437 (1902) (also 

stating that “any description which is sufficient to apprise 

[steel manufacturers] in the language of the art of the 

definite feature of the invention, and to serve as a warning 

to others of what the patent claims as a monopoly, is 

sufficiently definite to sustain the patent”).5 

—————— 

5See also Eibel Process Co. v. Minnesota & Ontario Paper Co., 261 
 

 

 

 

 

10 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

At the same time, a patent must be precise enough to

afford clear notice of what is claimed, thereby “‘appris[ing] 

the public of what is still open to them.’” Markman, 517 

U. S., at 373 (quoting McClain v. Ortmayer, 141 U. S. 419, 

424 (1891)).6 Otherwise there would be “[a] zone of uncertainty which enterprise and experimentation may enter

only at the risk of infringement claims.” United Carbon 

Co. v. Binney & Smith Co., 317 U. S. 228, 236 (1942). And 

absent a meaningful definiteness check, we are told, patent applicants face powerful incentives to inject ambiguity into their claims. See Brief for Petitioner 30–32 (citing 

patent treatises and drafting guides). See also Federal 

Trade Commission, The Evolving IP Marketplace: Aligning Patent Notice and Remedies With Competition 85

(2011) (quoting testimony that patent system fosters “an

incentive to be as vague and ambiguous as you can with 

your claims” and “defer clarity at all costs”).7 Eliminating

that temptation is in order, and “the patent drafter is in 

the best position to resolve the ambiguity in . . . patent 

—————— 

U. S. 45, 58, 65–66 (1923) (upholding as definite a patent for an improvement to a paper-making machine, which provided that a wire be 

placed at a “high” or “substantial elevation,” where “readers . . . skilled

in the art of paper making and versed in the use of the . . . machine” 

would have “no difficulty . . . in determining . . . the substantial [elevation] needed” for the machine to operate as specified). 6See also United Carbon Co. v. Binney & Smith Co., 317 U. S. 228, 

236 (1942) (“The statutory requirement of particularity and distinctness in claims is met only when they clearly distinguish what is

claimed from what went before in the art and clearly circumscribe what 

is foreclosed from future enterprise.”); General Elec. Co. v. Wabash 

Appliance Corp., 304 U. S. 364, 369 (1938) (“The 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.”). 7Online at http: //www. ftc.gov / sites /default/files /documents / 

reports/evolving-ip-marketplace-aligning-patent-notice-and-remediescompetition-report-federal-trade/110307patentreport.pdf (as visited

May 30, 2014, and available in Clerk of Court’s case file). 
 

 

Cite as: 572 U. S. ____ (2014) 11 

Opinion of the Court 

claims.” Halliburton Energy Servs., Inc. v. M–I LLC, 514 

F. 3d 1244, 1255 (CA Fed. 2008). See also Hormone Research Foundation, Inc. v. Genentech, Inc., 904 F. 2d 1558, 

1563 (CA Fed. 1990) (“It is a well-established axiom in 

patent law that a patentee is free to be his or her own

lexicographer . . . .”). 

To determine the proper office of the definiteness command, therefore, we must reconcile concerns that tug in

opposite directions. Cognizant of the competing concerns, 

we read §112, ¶2 to require that a patent’s claims, viewed 

in light of the specification and prosecution history, inform 

those skilled in the art about the scope of the invention 

with reasonable certainty. The definiteness requirement,

so understood, mandates clarity, while recognizing that

absolute precision is unattainable. The standard we adopt 

accords with opinions of this Court stating that “the certainty which the law requires in patents is not greater

than is reasonable, having regard to their subject-matter.” 

Minerals Separation, Ltd. v. Hyde, 242 U. S. 261, 270 

(1916). See also United Carbon, 317 U. S., at 236 (“claims 

must be reasonably clear-cut”); Markman, 517 U. S., at 

389 (claim construction calls for “the necessarily sophisticated analysis of the whole document,” and may turn on

evaluations of expert testimony). 

B 

In resolving Nautilus’ definiteness challenge, the Federal Circuit asked whether the ’753 patent’s claims were

“amenable to construction” or “insolubly ambiguous.”

Those formulations can breed lower court confusion,8 for 

—————— 

8See, e.g., Every Penny Counts, Inc. v. Wells Fargo Bank, N. A., ___ 

F. Supp. 2d ___, ___, 2014 WL 869092, *4 (MD Fla., Mar. 5, 2014)

(finding that “the account,” as used in claim, “lacks definiteness,” 

because it might mean several different things and “no informed and 

confident choice is available among the contending definitions,” but 

that “the extent of the indefiniteness . . . falls far short of the ‘insoluble 
 

12 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

they lack the precision §112, ¶2 demands. It cannot be 

sufficient that a court can ascribe some meaning to a

patent’s claims; the definiteness inquiry trains on the

understanding of a skilled artisan at the time of the patent application, not that of a court viewing matters 

post hoc. To tolerate imprecision just short of that rendering a claim “insolubly ambiguous” would diminish the 

definiteness requirement’s public-notice function and 

foster the innovation-discouraging “zone of uncertainty,” 

United Carbon, 317 U. S., at 236, against which this Court 

has warned. 

Appreciating that “terms like ‘insolubly ambiguous’ may 

not be felicitous,” Brief for Respondent 34, Biosig argues

the phrase is a shorthand label for a more probing inquiry 

that the Federal Circuit applies in practice. The Federal 

Circuit’s fuller explications of the term “insolubly ambiguous,” we recognize, may come closer to tracking the statutory prescription. See, e.g., 715 F. 3d, at 898 (case below) 

(“[I]f reasonable efforts at claim construction result in a 

definition that does not provide sufficient particularity

and clarity to inform skilled artisans of the bounds of the 

claim, the claim is insolubly ambiguous and invalid for 

indefiniteness.” (internal quotation marks omitted)). But 

although this Court does not “micromanag[e] the Federal 

Circuit’s particular word choice” in applying patent-law 

doctrines, we must ensure that the Federal Circuit’s test is 

at least “probative of the essential inquiry.” WarnerJenkinson Co. v. Hilton Davis Chemical Co., 520 U. S. 17, 

40 (1997). Falling short in that regard, the expressions 

“insolubly ambiguous” and “amenable to construction”

permeate the Federal Circuit’s recent decisions concerning

§112, ¶2’s requirement.9 We agree with Nautilus and its 

—————— 

ambiguity’ required to invalidate the claim”). 9 E.g., Hearing Components, Inc. v. Shure Inc., 600 F. 3d 1357, 1366 

(CA Fed. 2010) (“the definiteness of claim terms depends on whether 
 

Cite as: 572 U. S. ____ (2014) 13 

Opinion of the Court 

amici that such terminology can leave courts and the

patent bar at sea without a reliable compass.10 

IV 

Both here and in the courts below, the parties have

advanced conflicting arguments as to the definiteness of 

the claims in the ’753 patent. Nautilus maintains that the 

claim term “spaced relationship” is open to multiple interpretations reflecting markedly different understandings of 

—————— 

those terms can be given any reasonable meaning”); Datamize, LLC v. 

Plumtree Software, Inc., 417 F. 3d 1342, 1347 (CA Fed. 2005) (“Only 

claims ‘not amenable to construction’ or ‘insolubly ambiguous’ are

indefinite.”); Exxon Research & Engineering Co. v. United States, 265 

F. 3d 1371, 1375 (CA Fed. 2001) (“If a claim is insolubly ambiguous, 

and no narrowing construction can properly be adopted, we have held 

the claim indefinite.”). See also Dept. of Commerce, Manual of Patent

Examining Procedure §2173.02(I), p. 294 (9th ed. 2014) (PTO manual

describing Federal Circuit’s test as upholding a claim’s validity “if some 

meaning can be gleaned from the language”). 10The Federal Circuit suggests that a permissive definiteness standard “ ‘accord[s] respect to the statutory presumption of patent validity.’ ” 

715 F. 3d 891, 902 (2013) (quoting Exxon Research, 265 F. 3d, at 1375). 

See also §282, ¶1 (“[a] patent shall be presumed valid,” and “[t]he

burden of establishing invalidity of a patent or any claim thereof shall

rest on the party asserting such invalidity”); Microsoft Corp. v. i4i Ltd. 

Partnership, 564 U. S. ___, ___ (2011) (slip op., at 1) (invalidity defenses

must be proved by “clear and convincing evidence”). As the parties 

appear to agree, however, this presumption of validity does not alter

the degree of clarity that §112, ¶2 demands from patent applicants; to

the contrary, it incorporates that definiteness requirement by reference. See §282, ¶2(3) (defenses to infringement actions include 

“[i]nvalidity of the patent or any claim in suit for failure to comply with

. . . any requirement of [§112]”).

The parties nonetheless dispute whether factual findings subsidiary

to the ultimate issue of definiteness trigger the clear-and-convincingevidence standard and, relatedly, whether deference is due to the PTO’s 

resolution of disputed issues of fact. We leave these questions for 

another day. The court below treated definiteness as “a legal issue 

[the] court reviews without deference,” 715 F. 3d, at 897, and Biosig has

not called our attention to any contested factual matter—or PTO

determination thereof—pertinent to its infringement claims. 
 

 

 

 

14 NAUTILUS, INC. v. BIOSIG INSTRUMENTS, INC. 

Opinion of the Court 

the patent’s scope, as exemplified by the disagreement 

among the members of the Federal Circuit panel.11 Biosig

responds that “spaced relationship,” read in light of the

specification and as illustrated in the accompanying drawings, delineates the permissible spacing with sufficient

precision.

“[M]indful that we are a court of review, not of first

view,” Cutter v. Wilkinson, 544 U. S. 709, 718, n. 7 (2005),

we decline to apply the standard we have announced to 

the controversy between Nautilus and Biosig. As we have 

explained, the Federal Circuit invoked a standard more

amorphous than the statutory definiteness requirement 

allows. We therefore follow our ordinary practice of remanding so that the Court of Appeals can reconsider,

under the proper standard, whether the relevant claims in

the ’753 patent are sufficiently definite. See, e.g., Johnson 

v. California, 543 U. S. 499, 515 (2005); Gasperini v. Center for Humanities, Inc., 518 U. S. 415, 438 (1996). 

* * * 

For the reasons stated, we vacate the judgment of the

United States Court of Appeals for the Federal Circuit and

remand the case for further proceedings consistent with 

this opinion. 

It is so ordered. 

—————— 

11Notably, however, all three panel members found Nautilus’ arguments unavailing. 
Opinion of the Court 

Cite as: 572 U. S. ____ (2014) 15 

Appendix to opinion of the Court 

APPENDIX 

Patent No. 5,337,753, Figure 1