Definiteness

In linguistics, definiteness is a semantic feature of noun phrases that distinguishes between referents or senses that are identifiable in a given context and those that are not. 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. Still other languages, such as Danish, mark definiteness morphologically by changing the noun itself, manden ).

Definiteness as a grammatical category

There are times when a grammatically marked definite noun phrase 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 and a non-discrete category."

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, typically mark a noun phrase as indefinite. Others, including the, that, and genitive noun phrases 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 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.
In Danish, definiteness is marked morphologically.
In Romanian:
In Albanian definiteness is marked by a noun affix.
In Arabic, the definite can be determined from the indefinite with presence of the definitive article al- or a possessive pronoun suffix forming an iḍāfa construction. Adjectives describing definite nouns are also marked with the definitive article al-. الكتاب الكبير with two instances of al-
in Hungarian, verbs show agreement with the definiteness of their object:
in Erzya-Mordvin, verbs exhibit definite conjugation through personal-pronoun-based suffixes, while noun definiteness is marked by suffixes derived from demonstrative pronouns :
Japanese, 私は本を持っている, is ambiguous between definite and indefinite readings.

Germanic, Romance, Celtic, Semitic, and auxiliary languages generally have a definite article, often preposed but in some cases postposed. For example, Hebrew prefixes the letter he, while Aramaic suffixes the letter aleph. Many other languages do not. Some examples are Chinese, Japanese, Finnish, and modern Slavic languages except Bulgarian and Macedonian. When necessary, languages of this kind may indicate definiteness by other means such as demonstratives.
In most languages, definiteness is marked only on common nouns, since proper nouns are already considered inherently definite. However, Biblical Hebrew shows exceptions where the definite article can be prefixed to proper nouns. This demonstrates that, unlike in most languages, Biblical Hebrew may apply overt definiteness even to proper names, possibly for emphasis or specificity.
It is common for definiteness to interact with the marking of case in certain syntactic contexts. In many languages, a direct object receives distinctive marking only if it is definite. For example, in Turkish, the direct object in the sentence adamı gördüm is marked with the suffix -ı. The absence of the suffix on a direct object in Turkish means that it is indefinite and, in the absence of the indefinite article bir, no longer explicitly singular: adam gördüm.
In Serbo-Croatian, in the Baltic languages Latvian and Lithuanian, and, to a lesser extent in Slovene, definiteness can be expressed morphologically on prenominal adjectives. The short form of the adjective is interpreted as indefinite, while the long form is definite or specific:

short : Serbo-Croatian nov grad "a new city"; Lithuanian balta knyga "a white book"; Latvian balta māja "a white house"
long : novi grad "the new city, a certain new city"; baltoji knyga "the white book, a certain white book"; baltā māja, with a long vowel "the white house"

In some languages, the definiteness of the object affects the transitivity of the verb. In the absence of peculiar specificity marking, it also tends to affect the telicity of mono-occasional predications.
In some Scandinavian languages, such as Swedish, definite nouns inflect with a dedicated set of suffixes. This is known in Swedish as the grammatical category of species.