- This seventh edition of the Roget"s International Thesaurus is the most up-to-date edition of the world"s bestselling thesaurus - and the only thesaurus based on Peter Roget"s original reference classic of 1852. With more than 325,000 words, including over 2,000 words and phrases newly added since the 2001 edition, Roget"s International Thesaurus, 7th Edition truly stands out from the competition.