What is one of the three words, a, an, the, used before nouns to limit or define their application. A (or an) is called the indefinite article, the the definite article called?

article — (Gram.) One of the three words, a, an, the, used before nouns to limit or define their application. A (or an) is called the indefinite article, the the definite article. (Webster's 1913.)