ABSTRACTWhat does the word chair mean? How does the category of objects bearing this name differ between adults and pre-school children? And how does the knowledge of a possible function of an object affect subjects' judgements? Answers to these questions were sought by means of sorting and rank ordering tasks. Subjects were shown drawings of a variety of objects on which one could sit, and were asked to indicate which ones they would call chairs. Those objects so judged to be category members were rank ordered for degree of typicality (or ‘best example’) by a paired-comparisons procedure. Half the subjects saw drawings of the objects alone, while the others saw a person sitting on each object. The results revealed that adults consistently judged some objects to be better examples than others, and that the provision of function information affected the judgements in a characteristic way. A different, less stable typicality structure was found in the children's category. Function cues caused the children's rank order judgements to change greatly. These findings are discussed within the framework of some recent theories of lexical concept formation in young children, and in relation to recent work on the nature of internal representations.