In a patent or patent application, the claims define in technical terms the extent, i.e. the scope, of the protection conferred by a patent, or the protection sought in a patent application. The claims particularly point out the subject matter which the inventor(s) regard as their invention. United States Patent and Trademark Office (USPTO) Manual of Patent Examining Procedure (MPEP), Ninth ed., Rev. 01.2024, §2173 ("Claims Must Particularly Point Out and Distinctly Claim the Invention"), https://www.uspto.gov/web/offices/pac/mpep/s2173.html (accessed 04 Jan. 2025) In other words, the purpose of the claims is to define which subject matter is protected by the patent (or sought to be protected by the patent application). This is termed as the "notice function" of a patent claim—to warn others of inventor rights and infringement liability.See, e.g., PSC Computer Prods., Inc. v. Foxconn Int’l, Inc., 355 F.3d 1353, 1358 (Fed. Cir. 2004) ("One important purpose of the written description is to provide notice to the public as to the subject matter of the patent, while the claim provides notice as to the scope of the invention."). See also Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. __, 134 S. Ct. 2120 (2014) ("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' [citation omitted] against which this Court has warned."); McClain v. Ortmayer, 141 U.S. 419, 424 (1891) (a patent claim must be precise and clear enough to give the public clear notice of what is claimed, thereby "appris[ing] the public of what is still open to them"). The claims are of paramount importance in both prosecution and litigation.
For instance, a claim could read: "An apparatus for catching mice, said apparatus comprising a base, a spring member coupled to the base, and ..." "A chemical composition for cleaning windows, said composition substantially consisting of 10–15% ammonia, ..." "Method for computing future life expectancies, said method comprising gathering data including X, Y, Z, analyzing the data, comparing the analyzed data results..."
Background
In most jurisdictions, a patent is a right to exclude others from making, using, importing, selling or offering for sale the subject matter defined by the claims when the claim is for a thing (apparatus, composition of matter, system, etc.). If a claim is for a method, the right to exclude would be to exclude any single party from carrying out all the steps of the claim. In order to exclude someone from using a patented invention, the patent owner, or patentee, needs to demonstrate in a court proceeding that what the other person is using falls within the scope of a claim of the patent; therefore, it is more valuable to obtain claims that include the minimal set of limitations that differentiate an invention over what came before (i.e., the so-called prior art). But the fewer the limitations in a claim, the more likely it is that the claim will cover, or "read on", what came before and be rejected during examination or found to be invalid at a later time for obviousness or lack of novelty.
History
Patents have not always contained claims. In many European countries, patents did not contain claims until the 1970s. Before that time, it was often difficult to decide whether a product infringed a patent, since the sole basis to know the extent of protection was the description, in view of the prior art.
Interestingly, American inventors started using claims in their patent applications decades before the authorities (either judicial or legislative) started to require claims in patents. The first person who used in a US patent application the term "claim" in its current meaning is believed to be Isaiah Jennings in 1807.Restored Patents, Vol. 2, p. 161. cited from: Evolution of the Claims of U. S. Patents. 1938. Journal of the Patent Office Society. 20/2, 134-56,. K.B. Lutz. https://heinonline.org/HOL/Page?public=true&handle=hein.journals/jpatos20&div=20&start_page=134&collection=journals&set_as_cursor=0&men_tab=srchresults Claims were recommended in published patents in the Third Patent Act (1836) and finally became mandatory in the Fourth Patent Act (1870).
However, even among patent legal systems in which the claims are used as the reference to decide the scope of protection conferred by a patent, the way the claims are used may vary substantially. Traditionally, two types of claiming systems exist: the "central claiming system", according to which the claims identify the "centre" of the patented invention. The exact scope of the protection depends on the actual nature of the inventor's contribution to the art in the concerned technology. the "peripheral claiming system", according to which the claims identify the exact periphery, or boundary, of the conferred protection. In this system, the burden of drafting good claims is much higher on the patent applicant (or on his or her counsel). The applicant receives the protection he or she requested and almost nothing more, provided that the invention is new and non-obvious. This theoretically makes it easier for third parties to examine whether infringement may exist or not.
No patent system today is a purely either central or peripheral, but the system used in Germany and most of the other countries of continental Europe is considered more central than the system currently used in the United Kingdom, the United States, and especially Japan, which are more peripheral.Peter Groves, A Dictionary of Intellectual Property Law, , p. 51. In recent years, Japan's system has become more peripheral,See Decision of Supreme Court of Japan (Saikou Saibansho), February 24, 1998 Case No. Heisei 6 (o) 10831No. Heisei 6 (o) 1083, first recognizing the doctrine of equivalents. while the system used in the United States was becoming more central because of the increasing resort in US patent litigation to the doctrine of equivalents to expand claim scope unpredictably,See Dennis Crouch, Doctrine of Equivalents: What Elements Are you Narrowing?, Patently-O (Sept. 30, 2014) ("In a prior generation patentees could typically get to a jury with an allegation of infringement doctrine of equivalents. However, the court has simultaneously tightened the rules for DOE infringement and loosened the rules summary judgment — result being that infringement under the doctrine of equivalents is now regularly a summary judgment issue."); Ray D. Weston, A Comparative Analysis of the Doctrine of Equivalents: Can European Approaches Solve an American Dilemma?, 39 J.L. & Tech. 35, 35-36 (1998) ("One perceived source of uncertainty and unpredictability in patent law is the doctrine of equivalents. Originally intended to provide inventors with a fair scope of protection for their patents, it has become a powerful means of extending a patent's scope, often in unpredictable ways."). until the US Supreme Court reversed that trend in the Warner-Jenkinson case in 1997.See Warner-Jenkinson v. Hilton Davis, 520 U.S. 17 (Fed. Cir. 1997) (restricting the scope of the doctrine of equivalents.)
Requirements and structure In most modern patent laws, patent applications must have at least one claim, which are critical defining elements of the patent and the primary subject of examination. In some patent laws however, a date of filing may be obtained for an application which does not contain any claim.See for instance .
European Patent Convention
Under the European Patent Convention (EPC), a claim must define the matter for which the protection is sought in terms of technical features., The convention itself pertains to a procedure to secure a European patent. These technical features can be either structural (e.g. a nail, a rivet) or functional (e.g. fastening means).: "Technical features."
Regarding the structure of a claim, under the EPC, what is called the "preamble" is different from the meaning the "preamble" has under U.S. patent law. In an independent claim in Europe, the preamble is everything which precedes the expression "characterized in that" or "characterized by" in a claim written according to the so-called "two-part form", and therefore everything which is regarded as known in combination within one prior art document, namely the closest prior art document. (previously ) and, for instance, EPO board of appeal Decision T 13/84, Headnote 1. For this reason, in Europe, the preamble of a claim is sometimes also called "pre-characterizing portion".See for instance "The pre-characterising portion of the claim is based on..." in Decision T 0443/11 of 30 January 2012, item 2.1.
United States A claim may include the following parts:
A preamble that recites the class of the invention, and optionally its primary properties, purpose, or field: "An apparatus..." "A therapeutic method for treating cancer..." "A composition having an affinity for protein X..." This preamble may also reference another claim and refine it, e.g., "The method of claim 1..." (See "dependent claim" below.). A "transitional" phrase that characterizes the elements that follow. The phrases "comprising", "containing" and "including" are most often used and (under some patent laws, specifically US) preferable, as it means "having at least the following elements..." and are therefore open (inclusive) and do not exclude additional limitations. The phrases "consisting of" and "consisting essentially of" are (under some patent laws, specifically US) more limiting, as they mean "having all and only" or "virtually only" and are therefore closed (exclusive). In the US, the phrase "consisting of" excludes additional limitations, while the phrase "consisting essentially of" excludes additional limitations that would "materially affect the basic and novel characteristic(s) of the claimed invention". A set of "limitations" that together describe the invention: "an X, a Y, and a Z connected to the X and the Y." The elements should be described as though they interact or cooperate to achieve the desired result.Google Books Jeffrey G. Sheldon, How To Write a Patent Application sec. 6.3.5.3 (1992); see American Choc. Mach. Co. v. Helmstetter, 142 Fed. 978, 980 (2d Cir. 1905) ("The distinction between a combination and an aggregation lies in the presence or absence of mutuality of action. To constitute a combination it is essential that there should be some joint operation performed by its elements, producing a result due to their joint and co-operating action, while in an aggregation there is a mere adding together of separate contributions, each operating independently of the other. Defendant's machine comprises merely an aggregation of two devices. There is no mechanical or functional mutuality of operation. It is not a combination because there is no co-operation between the coating and jarring mechanisms, because the two devices do not unitedly perform their functions, and because they are not necessarily combined in one machine, and do not act together to secure the final result.") (citations omitted).