MPEP 2173: Indefiniteness Under 35 U.S.C. 112(b)

Answer in brief

MPEP 2173 requires claims to particularly point out and distinctly claim the invention under 35 U.S.C. 112(b). During examination, a claim is indefinite if its language is ambiguous, vague or unclear. That is a lower bar for rejection than the courts' "reasonable certainty" test (Nautilus) for issued patents.

What MPEP 2173 covers

The section's subsections address the specific claim drafting problems that draw § 112(b) rejections.

Breadth is not indefiniteness (2173.04).
New terminology (2173.05(a)); relative terminology and terms of degree (2173.05(b)); numerical ranges (2173.05(c)).
Exemplary claim language such as "for example" (2173.05(d)); lack of antecedent basis (2173.05(e)).
Functional limitations (2173.05(g)); alternative limitations (2173.05(h)); negative limitations (2173.05(i)).

How examiners use it

The examiner should explain why the term is unclear and, ideally, suggest a fix. Many § 112(b) rejections are resolved by amendment.

On the patent bar

Know that breadth is not indefiniteness, the antecedent basis rule, and the treatment of relative terms.

Read the full text

Official title: Claims Must Particularly Point Out and Distinctly Claim the Invention [R-10.2019].

Read MPEP 2173 in full on Wysebridge ↗

Or at the source: USPTO MPEP § 2173.

Sources for this entry

USPTO — MPEP § 2173 USPTO
Official text of this section, Ninth Edition, Revision 01.2024.
Wysebridge MPEP Center Wysebridge (publisher of this site)
The full MPEP (9th Ed., Rev. 01.2024) free to read, with Wysebridge's estimated patent bar weight for each chapter.

Practical guidance is original editorial content. Company-published figures are the company's own claims and are labeled as such.

Continue this reading path

MPEP 2181: Means-Plus-Function Under 35 U.S.C. 112(f)MPEP 2111: Broadest Reasonable Interpretation (BRI)MPEP 2163: Written Description Requirement

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Cite or share this entry

MPEP.net. “MPEP 2173: Indefiniteness Under 35 U.S.C. 112(b).” Wysebridge Reference. Content reviewed 9 November 2026.
https://mpep.net/mpep-2173/