# Written description

A requirement under 35 USC § 112 that an inventor must demonstrate, through the specification, that they actually possessed the claimed invention at the time of filing — not just that they had a vague idea. Written description is separate from enablement: enablement asks whether the reader can make the invention; written description asks whether the inventor had already conceived it. Failing the written description requirement is common when inventors try to add new matter to a continuation.

**Full entry:** https://patentbrief.org/glossary/written-description

**All patent terms:** https://patentbrief.org/glossary

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_Source: PatentBrief — https://patentbrief.org. A plain-English glossary of US patent terms._