National Thesaurus Day

Celebrated on 01/18/2026

Quick Fact

National Thesaurus Day is celebrated on January 18th, the birthday of Peter Mark Roget, the creator of Roget's Thesaurus. Roget began compiling his thesaurus in 1805, but it wasn't published until 1852, when he was 73 years old.

Origins and Establishment of National Thesaurus Day

National Thesaurus Day was created to honor Peter Mark Roget, who was born on January 18, 1779. Roget was a British physician, natural theologian, and lexicographer who published the first thesaurus in 1852. The day was established by the company that now publishes Roget's Thesaurus, likely in the late 20th or early 21st century, to promote vocabulary expansion and the love of words.

Evolution and Modern Commemoration

Initially, National Thesaurus Day was celebrated primarily by word enthusiasts, libraries, and educational institutions. Today, it has gained traction on social media, with people sharing their favorite synonyms and word games. Many schools use the day to teach students how to use a thesaurus effectively, and bookstores often host events or offer discounts on reference books.

Facts & General Observations

• Roget's Thesaurus has never been out of print since its first publication in 1852.
• The word "thesaurus" comes from the Greek word "thēsauros," meaning "treasure" or "storehouse."
• The first edition of Roget's Thesaurus contained 15,000 words; today's editions contain over 300,000.

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