National Thesaurus Day

National Thesaurus Day, observed January 18th, honors Peter Mark Roget, the British physician and scholar born on this date in 1779 who created Roget's Thesaurus, first published in 1852 under the full title "Thesaurus of English Words and Phrases Classified and Arranged so as to Facilitate the Expression of Ideas." Unlike a dictionary, which defines words, Roget organized his thesaurus by grouping words according to related concepts and ideas, a classification system reflecting his broader scientific and taxonomic interests as a doctor and secretary of the Royal Society. Roget reportedly began compiling word lists as a personal habit to combat depression and organize his thoughts, only publishing the finished work later in life, at age 73. The book was an immediate success and has remained continuously in print and revised ever since, becoming a standard writing reference alongside the dictionary. On National Thesaurus Day, word lovers, writers, and students celebrate by exploring synonyms, playing word games, learning new vocabulary, or simply flipping through a physical or digital thesaurus to appreciate the richness and precision it can bring to writing.