In linguistics, a grammatical gender system is a specific form of a noun class system, where nouns are assigned to gender categories that are often not related to the real-world qualities of the entities denoted by those nouns. In languages with grammatical gender, most or all nouns inherently carry one value of the called gender; the values present in a given language (of which there are usually two or three) are called the genders of that language.
Whereas some authors use the term "grammatical gender" as a synonym of "noun class", others use different definitions for each; many authors prefer "noun classes" when none of the inflections in a language relate to sex or gender. According to one estimate, gender is used in approximately half of the world's languages. According to one definition: "Genders are classes of nouns reflected in the behaviour of associated words."
Languages with grammatical gender usually have two to four different genders, but some are attested with up to 20.
Common gender divisions include masculine and feminine; masculine, feminine, and neuter; or animate and inanimate.
Depending on the language and the word, this assignment might bear some relationship with the meaning of the noun (e.g. "woman" is usually feminine), or may be arbitrary.
In a few languages, the assignment of any particular noun (i.e., nominal lexeme, that set of noun forms inflectable from a common lemma) to one grammatical gender is solely determined by that noun's meaning (or attributes, like biological sex, humanness, or animacy). However, the existence of words that denote male and female, such as the difference between "aunt" and "uncle" is not enough to constitute a gender system.
In other languages, the division into genders usually correlates to some degree, at least for a certain set of nouns (such as those denoting humans), with some property or properties of the things that particular nouns denote. Such properties include animacy or inanimacy, "humanness" or non-humanness, and biological sex.