In the prevailing linguistic literature, gender is considered as a morphosyntactic property to which agreement is sensitive. Gender is widespread in the world's languages; there are, however, many languages that lack it, though they may have systems of noun classification for reasons other than grammatical agreement. Gender agreement is an asymmetrical relation in the sense that one member of the agreement relation (the target) depends on the other member (the controller) for the gender property. The element that governs the relation (nouns and, in some languages, deictic pronouns) has lexical gender, though it is not necessarily arbitrary. Where nominal properties and agreement behaviour suggest different genders, agreement is the decisive indication of gender. The assignment of gender to nouns always has a nucleus in which semantics operates, above all grounded on distinctions of animacy, humanness and biological sex; yet often, formal criteria, either alone or together with semantics, determine gender ascription, with the possibility that the gender of some nouns remains unpredictable. In some languages, gender is expressed in the pronominal system only. Across the languages of the world, gender shows a great variety in the type of agreeing elements and also in the formal devices employed to mark it.