The papers in this volume are linked by a common concern, which is at the centre of current linguistic enquiry: how do we classify and categorize linguistic data, and how does this process add to our understanding of linguistic change? The scene is set by Aitchison’s paper on the development of linguistic categorization over the past few decades, followed by Biggam’s critical overview of theoretical developments in colour semantics. Lexical classification in action is discussed in papers by Fischer, Kay and Sylvester on the structures of thesauruses, while detailed treatments of particular semantic areas are offered by Kleparski, Mikołajczuk, O’Hare and Peters. Papers by Lass, Laing and Williamson, and Smith are concerned with the nature of linguistic evidence in the context of the historical record, offering new insights into text typology, scribal language and vowel classification. Much of the data discussed is new and original.