in·def·i·nite ar·ti·cle • n. Gram. a determiner (a and an in English) that introduces a noun phrase and implies that the thing referred to is nonspecific (as in she bought me a book; government is an art; he went to a public school). Typically, the indefinite article is used to introduce new concepts into a discourse. Compare with definite article.

INDEFINITE ARTICLE. In English grammar, the term for a and an when used to introduce a noun phrase: a cup of coffee or an angry reply. A occurs before consonant sounds (a garden, a human, a use) and an before vowel sounds (an orange, an hour, an uncle, an MP, an SOS). An is sometimes used before certain words beginning with an h, such as an hotel, an historian, particularly if the h is not pronounced. Some, however, pronounce the h, giving rise to controversy and being regarded by some others as slightly pretentious or precious. See ARTICLE, H.