Patent ambiguity is an uncertainty that clearly appears on the face of an instrument. Such an ambiguity will appear in the language of the document. In such documents, the court, reading the language in the light of all the facts and circumstances referred to in the instrument would not be able to derive therefrom the intention of the parties.
When used in the context of wills, patent ambiguity is an ambiguity appearing upon the face of the instrument, for example, a bequest to "some" of the six children of the testator's brother.
Patent ambiguity is also known as intrinsic ambiguity or ambiguitas patens.
The following is an example of a case law defining the term:
A patent ambiguity is that which appears on the face of the instrument, and arises from the defective, obscure, or insensible language used. In contrast, a latent ambiguity arises from extraneous or collateral facts which make the meaning of a written agreement uncertain although the language thereof, on its face, appears clear and unambiguous. [Allegheny Int'l v. Allegheny Ludlum Steel Corp., 40 F.3d 1416, 1424 (3d Cir. 1994)].