In patent law, a disclaimer are words identifying, in a claim, subject-matter that is not claimed[1] or another writing disclaiming rights ostensibly protected by the patent.
[2] By extension, a disclaimer may also mean the amendment consisting in introducing a negative limitation in an existing claim, i.e. "an amendment to a claim resulting in the incorporation therein of a 'negative' technical feature, typically excluding from a general feature specific embodiments or areas".
[3][4] The allowability of disclaimers is subject to particular conditions, which may vary widely from one jurisdiction to another.
[5] That right was subject to safeguards to make sure that the disclaimer was a true renunciation, rather than an extension of the monopoly.
§ 288 requires that the invalid claim be disclaimed before costs may be recovered.