What is a functional limitation in a patent claim?

A functional limitation in a patent claim is a term that recites a feature “by what it does rather than by what it is”. As stated in the MPEP, “A claim term is functional when it recites a feature ‘by what it does rather than by what it is’ (e.g., as evidenced by its specific structure or specific ingredients).”

Functional language is often used to define a particular capability or purpose served by an element, ingredient, or step in a process. It’s important to note that functional language is not inherently improper in patent claims.

To learn more:

• functional limitations
• patent claims
• claim language
• patent drafting