Does lack of antecedent basis always make a claim indefinite?

No, lack of antecedent basis does not always render a claim indefinite. According to MPEP 2173.05(e):

“Obviously, however, the failure to provide explicit antecedent basis for terms does not always render a claim indefinite. If the scope of a claim would be reasonably ascertainable by those skilled in the art, then the claim is not indefinite.”

The key factor is whether a person skilled in the art can reasonably understand the scope of the claim despite the lack of explicit antecedent basis. If the meaning is clear from context or inherent in the subject matter, the claim may still be considered definite.

To learn more:

• antecedent basis
• claim indefiniteness
• patent examination
• claim interpretation