Definition
The written description requirement means the specification must demonstrate that the inventor had possession of the full scope of the claimed invention at the time of filing.
Why It Matters Legally
This requirement prevents inventors from claiming more than they actually invented. It is a common tool for challenging claims that were broadened during prosecution beyond what the original filing supported.
Example Use Case
An applicant amends a claim to cover a feature never mentioned in the original filing, and the claim is rejected for lacking written description support.
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Related Terms
Enablement, Specification, Patent Claim, Priority Date, Patent Validity