Advertisement 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 the "notice function" of a patent claim--to warn others of what they must not do if they are to avoid infringement liability.[1] The claims are of the utmost importance both during prosecution and litigation alike.

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..." Advertisement