How do examiners evaluate functional limitations 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.

Examiners evaluate functional limitations in patent claims by considering several factors to determine if the language is sufficiently definite. The MPEP outlines three key considerations:

1. Whether there is a clear indication of the scope of the subject matter covered by the claim.
2. Whether the language sets forth well-defined boundaries of the invention or only states a problem solved or a result obtained.
3. Whether one of ordinary skill in the art would know from the claim terms what structure or steps are encompassed by the claim.

The MPEP states: “When a claim limitation employs functional language, the examiner’s determination of whether the limitation is sufficiently definite will be highly dependent on context (e.g., the disclosure in the specification and the knowledge of a person of ordinary skill in the art).”

Examiners also consider whether the functional limitation complies with the written description and enablement requirements of 35 U.S.C. 112(a), which is a separate issue from definiteness under 35 U.S.C. 112(b).