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 correlations with other grammatical categories. In addition, they differ in their semantics, in the way they develop, and in the way they become obsolescent and disappear. These parameters are the basis for the typology of classifiers presented here. This book is almost certainly the most substantial cross-linguistic account of classifiers ever published. Its range of exemplification includes major and minor languages from every continent (several from the author's own fieldwork). The work combines original research with innovative analysis and will interest typologists, those working in the field of morphosyntactic variation and lexical semantics, and exponents of formal theories who wish to explain the range of linguistic diversity found in natural language.