An article is a part of speech that is used with a noun to indicate the identifiability of the referent of the noun phrase). In English, there are two types of articles: definite and indefinite. The definite article is "the," and it is used to refer to a specific or particular noun. The indefinite articles are "a" and "an," and they are used to modify non-specific or non-particular nouns. Articles are part of a broader category called determiners, which also include demonstratives, possessive determiners, and quantifiers).

Articles typically specify the grammatical definiteness of the noun phrase, but in many languages, they carry additional grammatical information such as gender, number, and case). Articles can also modify anything that acts as a noun, such as a pronoun or a noun phrase. Often, a sentence needs an article before a noun in order to make grammatical sense.

For example, in the sentence "Nick bought a dog," the article "a" indicates that the word "dog" is a noun. Definite articles, such as "the," are used to refer to a particular member of a group, while indefinite articles, such as "a" or "an," do not refer to a specific identifiable entity).