Can applicants be their own lexicographers in patent claims?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Yes, applicants can be their own lexicographers in patent claims. According to MPEP 2173.01:

“A fundamental principle contained in 35 U.S.C. 112(b) or pre-AIA 35 U.S.C. 112, second paragraph is that applicants are their own lexicographers. They can define in the claims what the inventor or a joint inventor regards as the invention essentially in whatever terms they choose so long as any special meaning assigned to a term is clearly set forth in the specification.”

This means that inventors have the flexibility to use their own terminology or define terms in a specific way, as long as the meaning is clearly explained in the patent specification. However, it’s important to note that any special definitions must be explicitly stated in the specification to be considered during examination and potential litigation.