Roget's Thesaurus is a widely used English-language thesaurus, created in 1805 by Peter Mark Roget (1779–1869), British physician, natural theologian and lexicographer. It was released to the public on 29 April 1852. The original edition had 15,000 words, and each new edition has been larger. The Karpeles Manuscript Library Museum houses the original manuscript in its collection.