When is Thesaurus Day?

It is observed on January 18 each year.

How do people observe Thesaurus Day?

Explore new words and try using a thesaurus in writing.

Annual observance

Thesaurus Day

January 18 Cultural / community observance Updated 2026-04-22

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Overview

Thesaurus Day, observed annually on January 18th, commemorates the birth of Peter Mark Roget, the British physician and lexicographer who created *Roget's Thesaurus of English Words and Phrases*. The day encourages people to explore the vast world of synonyms, expand their vocabulary, and appreciate the indispensable tool a thesaurus provides for enhancing writing and communication.

Why it matters: Thesaurus Day, celebrated on January 18, honors the legacy of Peter Mark Roget, whose creation of the thesaurus transformed language by providing a rich resource for synonyms. This day highlights the importance of vocabulary in effective communication and encourages individuals to deepen their linguistic skills.

Origin and story

Peter Mark Roget was born on January 18, 1779, in London, England.

The word "thesaurus" comes from the Greek *thēsauros*, meaning "treasury" or "storehouse."

Quick facts

DateJanuary 18
TypeCultural / community observance
Great forFriends, Families, Classrooms, Teams

Also on this date

Ways to observe

Look up synonyms for common words.
Learn new descriptive terms.
Replace overused words in writing.
Improve writing clarity.
Experiment with tone and style.
Discover subtle differences between words.

Fun facts

Roget's Thesaurus was first published in 1852 and organized words by meaning rather than alphabetically.

Sources and attribution

Roget's Thesaurus Overview (Britannica)

External links may lead to third-party websites.

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FAQ

When is Thesaurus Day?: It is observed on January 18 each year.
What is Thesaurus Day?: Thesaurus Day, observed annually on January 18, commemorates the birth of Peter Mark Roget, the British physician and lexicographer who created *Roget's Thesaurus of English Words and Phrases*. The day encourages people to explore the vast world of synonyms, expand their vocabulary, and appreciate the indispensable tool a thesaurus provides for enhancing writing and communication.
How do people observe Thesaurus Day?: Explore new words and try using a thesaurus in writing.

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