This book explores the crosslinguistic distributional patterns of definiteness markers. A distinction is drawn between semantic definiteness and morpho-syntactic definiteness marking. The semantic components of definiteness are arranged, similar to semantic maps, and language-specifically assigned to definiteness markers. This model is based on the results of an empirical study of Q'ekchi', Otomi, Maori and Basque. The choice of a suitable sample for a typological study is also discussed.