In linguistics, grammatical gender is a specific form of noun-class system in which the division of noun classes forms an agreement system with another aspect of the language, such as adjectives, articles, pronouns, or verbs. This system is used in approximately one quarter of the world's languages. In these languages, most or all nouns inherently carry one value of the grammatical category called gender; the values present in a given language (of which there are usually two or three) are called the genders of that language. According to one definition: "Genders are classes of nouns reflected in the behaviour of associated words."