'pb ‘The vital centre of a language dictionary, the bulk of a terminological lexicon remains [...] the definition’ (Alain Rey). The dictionary ‘translates’ the language, by the infinite number of its definitions, one after the other, as in a film. Cataloguing words means defining them, classifying them in a mental order, giving them a value. The link between words and things is the subject of the definition from Aristote. This book illustrates its importance in any dictionary: the definition is at the centre of language, semantic to metalanguage, from synonymy to polyseaemia to speech. In the dictionary, the definition concerns practical and philosophical issues, language acts and the language itself. There is confirmation of Ferdinand de Saussure’s intuition: “The word, despite the difficulty of defining it, is a unit that is necessary in mind, something that is central to the language mechanism”. There is huge scope for research into the link between dictionary and definition.’/PB