Definite articles such as English the are used to refer to a particular member of a group or class. It may be something that the speaker has already mentioned or it may be otherwise something uniquely specified.
For example, Sentence 1 uses the definite article and thus expresses a request for a particular book. In contrast, Sentence 2 uses an indefinite article and thus conveys that the speaker would be satisfied with any book.
Give me the book.
Give me a book.
The definite article can also be used in English to indicate a specific class among other classes:
The cabbage white butterfly lays its eggs on members of the Brassica genus.
However, recent developments show that definite articles are morphological elements linked to certain noun types due to lexicalization. Under this point of view, definiteness does not play a role in the selection of a definite article more than the lexical entry attached to the article.[clarification needed][1][2]
Indefinite articleEdit
Indefinite articles are those such as English "some" or "a", which do not refer to a specific identifiable entity. Indefinites are commonly used to introduce a new discourse referent which can be referred back to in subsequent discussion:
A monster ate a cookie. His name is Cookie Monster.
Indefinites can also be used to generalize over entities who have some property in common:
A cookie is a wonderful thing to eat.
Indefinites can also be used to refer to a specific entities whose precise identity is unknown or unimportant.
A monster must have broken into my house last night and eaten all my cookies.
A friend of mine told me that happens frequently to people who live on Sesame Street.
Indefinites also have predicative uses:
Leaving my door unlocked was a bad decision.
Indefinite noun phrases are widely studied within linguistics, in particular because of their ability to take exceptional scope.