What is the ‘three-prong test’ for functional claim language?

The ‘three-prong test’ for functional claim language is a method used by the USPTO to determine whether a claim limitation expressed in functional language is sufficiently definite under 35 U.S.C. 112(b). According to MPEP 2173.05(g), the test involves the following three prongs:

1. Is there a clear cut indication of the scope of the subject matter covered by the claim?
2. Does the language set forth well-defined boundaries of the invention or only state a problem solved or a result obtained?
3. Would one of ordinary skill in the art know from the claim terms what structure or steps are encompassed by the claim?

The MPEP states: “The examiner should apply the following factors in making this determination: (1) whether there is a clear cut 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; and (3) whether one of ordinary skill in the art would know from the claim terms what structure or steps are encompassed by the claim.”

This test helps examiners assess whether functional language in a claim is sufficiently clear and definite to meet the requirements of 35 U.S.C. 112(b).

To learn more:

• three-prong test
• functional claim language
• USPTO
• patent examination
• 35 U.S.C. 112(b)