How does the USPTO determine if claim language is definite?

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 USPTO determines if claim language is definite by applying the following principles:

• Claims are reviewed from the perspective of one of ordinary skill in the art at the time of filing.
• Definiteness is evaluated in light of the content of the application disclosure, prior art of record, and claim interpretation that may be provided by prosecution history.
• Examiner focuses on whether the claim meets the threshold requirements of clarity and precision, not whether more suitable language could have been used.
• Only terms which are not understood or are subject to multiple plausible interpretations should be rejected as indefinite.

As stated in MPEP 2173.02: “The threshold requirement of clarity and precision must be balanced with the limitations of the language and the science.”