In linguistics, definiteness is a semantic feature of noun phrases, distinguishing between referents or senses that are identifiable in a given context (definite noun phrases) and those which 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 that the same expression could 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). In still other languages, such as Danish, definiteness is marked morphologically. Definiteness as a grammatical category There are times when a grammatically marked definite NP is not in fact identifiable. For example, the polar bear's habitat is the arctic does not refer to a unique, familiar, specific bear, in an example of a form-meaning mismatch. "The theoretical distinction between grammatical definiteness and cognitive identifiability has the advantage of enabling us to distinguish between a discrete (grammatical) and a non-discrete (cognitive) category."[p. 84] Use in different languages English In English, definiteness is usually marked by the selection of determiner. Certain determiners, such as a, an, many, and some, along with numbers (e.g., four items), typically mark a noun phrase as indefinite. Others, including the, that, and genitive noun phrases (e.g., my brother) typically mark the noun phrase as definite. A number of tests have been proposed to distinguish definite from indefinite noun phrases. "Each has a foundation in intuition, as well as some degree of grammatical effect. However, it is not clear that any of them corresponds cleanly to formal categories." If a noun phrase can be put into an existential clause such as there is noun phrase at the door (e.g., there are two wolves at the door), it is likely indefinite. "The concept of identifiability expressed by the definite article is best understood in terms of pre-empting a question with which?" Other languages In Basque, definiteness is marked by a phrasal clitic article. ("woman"), (woman-ART: "the woman"), (woman beautiful-ART: "the beautiful woman") In Danish, definiteness is marked morphologically. In Romanian: ("man"), (man-ART: "the man"), (man-ART good: "the good man") or (good-ART man: "the good man") In Albanian definiteness is marked by