§112 · Disclosure
Teach the invention, or lose the claim.
A patent is a bargain: a temporary monopoly in exchange for telling the public how the invention works. Section 112 is where you hold up your end — and where thin applications fall apart. These are the disclosure requirements your specification and claims must satisfy.
The requirements
What §112 demands
Each is a separate way an otherwise-novel, non-obvious invention can still be rejected — or invalidated years later.
Written description
§112(a)The specification must describe the invention in enough detail to show that you actually possessed the full invention as of your filing date — not merely that it would be desirable.
Watch · Claiming broadly (e.g. a whole genus) while the spec only describes a few examples. The claim outruns what you disclosed.
Enablement
§112(a)The specification must teach a person of ordinary skill how to make and use the full scope of the claimed invention without 'undue experimentation.' Courts weigh this with the Wands factors.
Watch · A broad claim the disclosure can't actually support across its whole range, so a skilled person would have to invent to fill the gaps.
Definiteness
§112(b)The claims must inform a skilled reader, with reasonable certainty, of the boundaries of the invention. The Supreme Court set this standard in Nautilus v. Biosig Instruments (2014).
Watch · Vague terms of degree ('about,' 'substantially'), inconsistent terminology, or a claim term with no clear meaning in the art.
Best mode
§112(a)At the time of filing, you must disclose the best way you actually knew to carry out the invention — you can't keep the optimal version secret while patenting a worse one.
Watch · Still required, but after the AIA a failure to disclose the best mode can no longer be used to invalidate or render unenforceable an issued claim.
Means-plus-function
§112(f)A claim element written purely as a function ('means for fastening…') is construed to cover only the specific structure disclosed in the specification, plus its equivalents.
Watch · Using functional language without disclosing corresponding structure — which can narrow the claim drastically or render it indefinite.
Check your draft
§112 is the fourth gate.
An invention must also be eligible (§101), novel (§102), and non-obvious (§103). For §112 itself, the claim tools catch the most common problems before an examiner does.
Plain-English education, not legal advice. Written-description and enablement disputes are among the most technical in patent law — for claims that matter, have a registered patent attorney draft and review the specification. PatentBrief is not a law firm.
FAQ
Specification (§112) — common questions
What is the enablement requirement?
Under §112(a), the patent specificationspecificationThe main body of the patent — describes the invention in detail. Used to interpret the claims.Read more → must teach a person of ordinary skill how to make and use the full scope of the claimed invention without 'undue experimentation.' A claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → broader than what the disclosure supports can be rejected or invalidated.
What is the written description requirement?
Also under §112(a): the specificationspecificationThe main body of the patent — describes the invention in detail. Used to interpret the claims.Read more → must describe the invention in enough detail to show that you actually possessed the full invention as of the filing datefiling dateThe day the patent application was submitted to the USPTO. Sets the priority date for prior-art comparisons.Read more → — not merely that it would be desirable to have.
What makes a patent claim indefinite?
Under §112(b), a claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → is indefinite if it fails to inform a skilled reader, with reasonable certainty, of the scope of the invention (Nautilus v. Biosig, 2014). Vague terms of degree and inconsistent terminology are common causes.
The four requirements