A noun may refer to a man, a woman, an animal, or an inanimate object of varied shape, size, and function, or have abstract reference. Noun categorization devices vary in their expression, and the contexts in which they occur. Large sets of numeral classifiers in South-East Asian languages occur with number words and quantifying expressions. Small highly grammaticalized noun classes and gender systems in Indo-European and African languages, and the languages of the Americas are expressed with agreement markers on adjectives, demonstratives, and also on the noun itself. Further means include noun classifiers, classifiers in possessive constructions, verbal classifiers, and two lesser-known types: locative and deictic classifiers. This introductory chapter offers a general typological background, focusing on issues in noun categorization devices particularly relevant for this volume.