What is the “approximation” term 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.

What is the “approximation” term in patent claims?

The term “approximation” in patent claims is a type of relative terminology that can be used to describe a range or value. According to MPEP 2173.05(b), “approximation” terms are acceptable in patent claims when the degree of precision appropriate for the subject matter is known to one of ordinary skill in the art. The MPEP states:

“The use of approximation terms or terms of degree such as “about,” “essentially,” “substantially,” is not indefinite when the specification provides some standard allowing for one of ordinary skill in the art to understand the scope of the term.”

However, it’s important to note that the use of “approximation” terms should be supported by the specification to avoid indefiniteness issues.