Patent claim

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. 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 what they must not do if they are to avoid infringement liability. 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..." 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. Patents have not always contained claims.