Almost all languages have some grammatical means for the linguistic categorization of nouns. Well-known systems such as the lexical numeral classifiers of South-East Asia, on the one hand, and the highly grammaticalized gender agreement classes of Indo-European languages, on the other, are the extremes of a contiuum. They can have a similar semantic basis, and one can develop from the other. Classifiers come in different morphological forms; they can be free nouns, clitics, or affixes. Some languages combine several varieties of classifiers. Different types of classifiers show varying correlat.