How does the MPEP treat terms of degree 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.

The MPEP addresses terms of degree in patent claims in MPEP 2173.05(b). Terms of degree are relative terms that require careful consideration to determine if they are definite. The MPEP states:

“Terms of degree are not necessarily indefinite. […] If the specification does not provide some standard for measuring that degree, a determination must be made as to whether one of ordinary skill in the art could nevertheless ascertain the scope of the claim (e.g., a standard that is recognized in the art for measuring the meaning of the term of degree).”

Examples of terms of degree include “substantially,” “about,” “approximately,” and “essentially.” The key to their acceptability is whether the specification provides enough guidance for a person of ordinary skill in the art to understand the scope of the invention with reasonable certainty. If not, the term may render the claim indefinite.