Use Of Term Definitions In Patent Applications

Toby H. Kusmer and Michael E. Fogarty, Partners of McDermott Will & Emery, LLP

11 minutes to read

This article is reprinted with permission from McDermott Will & Emery LLP from the Spring 2005,IP Review.

The authors address the key issues and risks to consider when using claim term definitions in patent applications and potential pitfalls to avoid when presenting definitions.

Patent drafters are well advised to keep in mind the ultimate purpose of their craft: to allow the patent holder to assert the patent rights against potential infringers, irrespecðtive of whether the ultimate goal is to prevent that party from making, using, selling or importing the claimed subject matter, or to generate revenue or other remuneration for the patent owner through licensing or some other transfer of intellectual property rights.

As the Federal Circuit often reminds us, a determination of patðent infringement involves a two-step process: interpretation or construction of the pertinent patent claims to define their scope of coverage; and determination of whether the properly conðstrued patent claims encompass the accused device or service.1 Only claims of a patent can be infringed. Neither the specificaðtion, which includes the written description of the invention, nor the drawings accompanying the specification, can be infringed.2 Thus, construction of a claim is necessary to define the metes and bounds of the protection afforded thereby. All limitations in a claim must be considered meaningful.3

Use the Specification to Craft a Desired Claim Term Definition

So what steps can a patent practitioner take to help make the outcome more likely to be favorable for the patent owner? To interpret the scope of claims, the courts look first to the so-called "intrinsic evidence," which sequentially includes the language of the patent claims themselves, the patent specification and the prosecution history, to ascertain the appropriate meaning of claim language.4 The language of the claims as it appears in the patent is controlðling, irrespective of how the owner of the patent may wish that language to read.5 The claim language is to be given its ordinary and accustomed meaning as one skilled in the art would interpret it, unless the inventor clearly demonstrated some other definiðtion should be used.6 Common canons of claim construction, likely familiar to the reader, include the concepts that words must be used consistently in the claims and specification7 and that the same term used in different places in the claims must be interpreted consistently.8 It is entirely within the sound disðcretion of the court as to whether other (extrinsic) evidence will be considered in determining the meaning of the claims. Such extrinsic evidence may include expert testimony concerning how those skilled in the art would interpret the claims.9

More and more frequently, infringement cases are won or lost depending upon how the claims are ultimately construed by the courts. The importance of intrinsic evidence used to interpret claim language was clearly demonstrated in a recent case from the Federal Circuit, in which the court held that dictionary definitions of terms used in claims are not preemptive of the intrinsic evidence surrounding the patent, as well as that courts are not permitted to disregard the intrinsic record when construðing claim language.10

Patent practitioners can exercise a great deal of influence in shaping the intrinsic record of an issued patent. One such tool at their disposal is the ability to define terms, especially those used in the claims. As is well established, "a patentee may choose to be his own lexicographer and use terms in a manner other than their ordinary meaning, as long as the special definition of the term is clearly stated in the patent specification or file history."11 Thus, the specification "may act as a sort of dictionary, which explains the invention and may define terms used in the claims."12 If inventors wish to change the meaning of a term from its ordinary meaning, however, they must clearly say so in the specification.13 "[I]t is always necessary to review the specificaðtion to determine whether the inventor has used any terms in a manner inconsistent with their ordinary meaning."14 Further, "[t]he prosecution history is often helpful in understanding the intended meaning as well as the scope of technical terms, and to establish whether any aspect thereof was restricted for purposes of patentability."15

Of course, use of such a tool is easier said than done. There are many factors to consider. Each of the tools available to the practitioner is subject to both benefits and risks. For example, a practitioner may define a term either more broadly or more narrowly than the ordinary meaning the term might suggest. Specification-embedded definitions may be used to broadly define a term used in a claim and, at the same time, explicitly exclude the prior art. This eliminates the need to include negaðtive limitations in the claim, a practice that is often frowned upon. Broad specification-embedded definitions are also useful in cases where the disclosure of the patent is limited to a single embodiment, often creating a context for narrow interpretation of claim language.

The Impact of Specification-Supplied Claim Term Definitions on the Infringement Analysis

Consider that infringement of a U.S. patent can occur in two ways: a device or process may "literally" infringe a patent claim, or, even if it does not literally infringe, it may infringe under the so-called doctrine of equivalents. A finding of literal infringeðment would require that the accused device or process embody every element of an asserted patent claim.16 The absence of even a single limitation precludes a finding of literal infringement.17

The doctrine of equivalents is an equitable doctrine, designed to relieve an inventor from a semantic strait jacket wherein insubðstantial changes may be made to the accused device or method from that of the claimed invention to avoid literal infringement. The doctrine provides that even if the accused device does not literally infringe the claims in issue, infringement may exist if the accused device is substantially equivalent to the claimed device.18 The doctrine thus invites patentees to teach equivalencies using claim term definitions.

The Risk Posed by Unknown Prior Art

However, using claim term definitions to exclude prior art or to teach equivalency does pose risks. The inventor (and by extenðsion the patent application drafter) is charged with knowledge of all relevant and material prior art, even possible prior art that was unknown to the patent drafter at the time the claims were drafted and at the time the distinctions between the claim language used and the known prior art was drawn (by claim term definitions) to withstand attacks on validity. Of course, it is a rare case in which the patent drafter is actually aware of all of the relevant prior art, even where a prior art search is perðformed before drafting the application. Patent practitioners are all well aware of the possibility that unknown prior art, such as subject matter that is in public use or on sale in the United States prior to the invention by the applicant or disclosed in obscure publications, e.g., an academic theses for which only one publicly available copy exists, will surface. Thus, when defining a term broadly (with the hope of providing a broad claim construction), the definition explicitly provided will overlap with the prior art. This risk is particularly draconian where the defined term is the only portion of the claim that distinguishes the claim from the prior art known at the time the claim was drafted.


An often-overlooked risk of including definitions in a patent application, even for terms not present in the claims, is the risk posed by the public disclosure-dedication doctrine. The public disclosure-dedication doctrine provides that a patent applicant is considered to have dedicated unclaimed subject matter to the public and cannot reclaim disclosed but unclaimed subject matter under the doctrine of equivalents. The Federal Circuit has held that when such disclosures are "specific," they are dedicated to the public, and when "general," they are not.19 For example, as a case in point, the patentee's disclosure of plastic for use as a resilient clip or strap was found to be specific and dedicated, while disclosure of "other resilient materials" was too general to have been dedicated to the public all resilient strap materials other than metal.


It is helpful to define terms in a patent application, particularly where they are used in the claims, but bearing in mind a number of important considerations.

How many embodiments are disclosed? The fewer embodiments, the greater the chance that undefined claim terms will be narrowly construed.

Does a particular feature that is to be described and claimed have any known equivalents? Defining terms as including various equivalents can be helpful in broadening the construction of the claims.

How much is known about the prior art? The less that is known, the greater the risk of writing a definition into the teeth of the prior art.

Is a single term being used in the claim to distinguish that term from the prior art? If so, great care should be taken to ensure that the term distinguishes the claim from the prior art, with an appreciation of the risk of unknown prior art surfacing that could invalidate the claim. In this situation, the general rule is that the patent drafter should include claims of various scope (that would have a better chance of surviving a validity challenge).

Is a defined term being used in the specification as well as the claims, or just in the specification, i.e., not in the claims? In the latter case, one should be aware of the possibilities of dedicating subject matter under the public disclosure-dedication doctrine.

"Specification-embedded definitions may be used to broadly define a term used in a claim and, at the same time, explicitly exclude the prior art."

1 Markman v. Westview Instruments, Inc., 52 F.3d 967, 976, (Fed. Cir. 1995) (en banc), aff'd., 116 S. Ct. 1384 (1996); Dawn Equip. Co. v. Kentucky Farms, Inc., 140 F.3d 1009 (Fed. Cir. 1998); Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448 (Fed. Cir. 1998) (en banc).

2 Multiform Desiccants, Inc. v. Medzan, Ltd., 133 F.3d 1473 (Fed. Cir. 1998); Shatterproof Glass Corp. v. Libbey-Owens Ford Co. , 758 F.2d 613, 625-26 (Fed. Cir.), cert. dismissed, 474 U.S. 976 (1985).

3 Lantech Inc. v. Keip Manuf. Co., 32 F.3d 542, 546 (Fed. Cir. 1994); Lemelson v. United States, 752 F.2d 1538, 1551 (Fed. Cir. 1985).

4 Vitronics Corp. v. Conceptronic, Inc. , 90 F.3d 1576, 1582, 39 USPQ2d 1573, 1576 (Fed. Cir. 1996).

5 Rolite, Inc. v. Wheelabrator Technologies, 903 F. Supp. 870, 872 (E.D. Pa. 1995).

6 Intellicall, Inc. v. Phonometrics, Inc., 952 F.2d 1384, 1387 (Fed. Cir. 1992); Envirotech Corp. v. Al George, Inc., 730 F.2d 753 (Fed. Cir. 1984); Fromson v. Advance Offset Plate, Inc., 720 F.2d 1565, 1571 (Fed. Cir. 1983).

7 Fonar Corp. v. J&J, 821 F.2d 627 (Fed. Cir. 1988).

8 Phonometrics v. Northern Telecom, 133 F.3d 1459 (Fed. Cir. 1998).

9 Markman v. Westview Instruments, 116 S.Ct. 40 (1995).

10 C.R. Bard, Inc. v. United States Surgical Corp., Case No. 004-1135 (Fed. Cir. Oct. 29, 2004).

11 Vitronics, 90 F.3d at 1582.

12 Markman, 52 F.3d at 979.

13 HoganasABv. Dresser Indus., Inc., 9 F.3d 948, 951 (Fed. Cir. 1993) (affirming summary judgment of noninfringement); Vitronics Corp., 90 F.3d at 1584 (Fed. Cir. 1996).

14 Northern Telecom, Ltd. v. Samsung Electronics Co., Ltd., 215 F.3d, 1281, 1293 (Fed. Cir. 2000), quoting Vitronics Corp., 90 F.3d at 1582 (Fed. Cir. 1996).

15 Vivid Technologies, Inc. v. American Science & Engineering, Inc., 200 F.3d 795, 804 (Fed. Cir. 1999)

16 Litton Sys., Inc. v. Honeywell, Inc., 140 F.3d 1449, 1454 (Fed. Cir. 1998); Read Corp. v. Portec, Inc., 970 F.2d 816, 822 (Fed. Cir. 1992); Laitram Corp. v. Rexnord, Inc., 939 F.2d 1533, 1535 (Fed. Cir. 1991); Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 4 USPQ 2d 1737 (Fed. Cir. en banc 1987).

17 Kahn v. General Motors Corp., 135 F.3d 1472 (Fed. Cir. 1998), cert. denied, 119 S. Ct. 177 (1998).

18 Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 610 (1950).

19 PSC Computer Prods., Inc. v. Foxconn Int'l, Inc., 355 F.3d 1353 (Fed. Cir. 2004)