It is well known that an article is a type of restrictive adjectives--that is, it limits the noun being described. The articles are perhaps the "simplest" adjectives --so simple that we often don't recognize that they are really adjectives. In English and Arabic, this is not so vital, but in French, it is; adjectives in French must agree in number and gender with the nouns they modify. The article is used with a noun showing whether the noun refers to something definite or indefinite. "Definite" means that "the" in English refers to some specific thing as contrasted with "a" or "an" which does not refer to one specific thing.