How does the preamble affect claim interpretation?

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 effect of the preamble on claim interpretation is determined on a case-by-case basis. As stated in MPEP 2111.02, “The determination of whether a preamble limits a claim is made on a case-by-case basis in light of the facts in each case; there is no litmus test defining when a preamble limits the scope of a claim.”

Generally, the preamble limits the claim if:

• It recites essential structure or steps
• It’s necessary to give life, meaning, and vitality to the claim
• It’s used to define the scope of the claimed invention

As the Federal Circuit stated in Bell Communications Research, Inc. v. Vitalink Communications Corp., “[A] claim preamble has the import that the claim as a whole suggests for it.”