This thesaurus is based on the system devised by Peter Roget for his original thesaurus of 1852. Words and phrases are arranged according to the ideas or concepts that they express within an overall system of categories and classes. Thus the user can start from an idea and explore different ways to express it. This fifth edition brings Roget's original category concept towards the 21st century. 325,000 words and phrases are grouped by concept into 1073 categories with all synonyms, antonyms and related words presented together for quick and easy reference. The text has been fully revised and expanded, including 31 entirely new categories, such as computers, fitness and exercise, and all kinds of sport. The whole range of language from archaisms to the latest slang (labelled) is included.