What is the difference between functional limitations and means-plus-function claim language?

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.

While both functional limitations and means-plus-function claim language describe elements by their function, there are important differences:

• Means-plus-function claims are a specific form of functional claiming authorized by 35 U.S.C. 112(f).
• Means-plus-function claims are interpreted more narrowly, limited to the structure disclosed in the specification and its equivalents.
• General functional limitations can be broader and are not necessarily limited to specific structures in the specification.

The MPEP clarifies: “Unlike means-plus-function claim language that applies only to purely functional limitations, Phillips v. AWH Corp., 415 F.3d 1303, 1311, 75 USPQ2d 1321, 1324 (Fed. Cir. 2005) (en banc) (‘Means-plus-function claiming applies only to purely functional limitations that do not provide the structure that performs the recited function.’), functional claiming often involves the recitation of some structure followed by its function.”