There are three articles used to describe nouns: ‘a’, ‘an’, and ‘the’. These are broken down into the definite article ‘the’ and the indefinite articles, ‘a’ and ‘an’. The definite article is used to describe something specific, whereas the indefinite articles describe something non-specific. The use of ‘a’ or ‘an’ depends upon whether the starting letter or starting sound of the noun is a vowel or vowel sound.