Specificity (linguistics) in the context of "Noun phrase"

In linguistics, definiteness is a semantic feature of noun phrases that distinguishes between referents or senses that are identifiable in a given context (definite noun phrases) and those that are not (indefinite noun phrases). The prototypical definite noun phrase picks out a unique, familiar, specific referent such as the sun or Australia, as opposed to indefinite examples like an idea or some fish.

There is considerable variation in the expression of definiteness across languages, and some languages such as Japanese do not generally mark it, so the same expression can be definite in some contexts and indefinite in others. In other languages, such as English, it is usually marked by the selection of determiner (e.g., the vs. a). Still other languages, such as Danish, mark definiteness morphologically by changing the noun itself (e.g. Danish en mand (a man), manden (the man)).