thir·​ty | \ˈthər-tē \
plural thirties

Definition of thirty 

1 : a number equal to three times 10 — see Table of Numbers

2 thirties plural : the numbers 30 to 39 specifically : the years 30 to 39 in a lifetime or century

3 : a sign of completion : end usually written 30 wrote thirty on the last page of the story

4 : the second point scored by a side in a game of tennis

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Other Words from thirty

thirtieth \ ˈthər-​tē-​əth \ adjective or noun
thirty adjective
thirty pronoun, plural in construction
thirtyish \ ˈthər-​tē-​ish \ adjective

Examples of thirty in a Sentence

The temperature outside is in the high thirties. He is in his thirties.

Recent Examples on the Web

The vast majority of extra-continentales are young men in their twenties and thirties who claim to be fleeing some danger back home. Lauren Markham, The New Republic, "How efforts to block refugees and asylum-seekers from Europe have only made the global migration crisis more complex and harrowing," 26 Feb. 2018 Nobukazu Kuriki, in his mid-thirties, fell ill and was descending on Monday when his team lost contact with him, his team said on Facebook. Bard Wilkinson, CNN, "Japanese climber Nobukazu Kuriki dies on eighth Everest attempt," 21 May 2018 Both in their thirties, the superstars are unlikely to return in Qatar in 2022. John Leicester,, "Winds of football change blow at Russia World Cup," 7 July 2018 The man, who is believed to be in his thirties, was shot in the area of Brookford and Dacia streets in Dorchester around 9:50 p.m., Boston police wrote on their website. Felicia Gans,, "One man dead, four others injured in two separate July 4 shootings in Dorchester," 5 July 2018 The two-minute-thirty-second clip went live December 31, 2015. Heran Mamo, Billboard, "XXXTentacion Discusses His History of Violence & Why He's Against Feminism in New Interview," 5 June 2018 His approval rating in most polls has moved up from the high thirties to the low forties. Ronald Brownstein, CNN, "Beating Republicans in November will be harder than Democrats thought," 22 May 2018 The thirties also brought revelations and violent political emergencies that plunged Locke into a rapprochement with the left. Tobi Haslett, The New Yorker, "The Man Who Led the Harlem Renaissance—and His Hidden Hungers," 11 May 2018 Next to him is a scruffy man in his thirties who has the chemical structure of dopamine tattooed on his left arm. Bruce Schoenfeld, WIRED, "Your Next Glass of Wine Might Be a Fake—and You'll Love It," 30 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'thirty.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of thirty

before the 12th century, in the meaning defined at sense 1

History and Etymology for thirty

Middle English thritty, from thritty, adjective, from Old English thrītig, from thrītig group of 30, from thrīe three + -tig group of ten; akin to Old English tīen ten

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Time Traveler for thirty

The first known use of thirty was before the 12th century

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More Definitions for thirty



English Language Learners Definition of thirty

: the number 30

thirties : the numbers ranging from 30 to 39

: a set of years ending in digits ranging from 30 to 39


thir·​ty | \ˈthər-tē \

Kids Definition of thirty

 (Entry 1 of 2)

: being three times ten



Kids Definition of thirty (Entry 2 of 2)

: three times ten : 30

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Comments on thirty

What made you want to look up thirty? Please tell us where you read or heard it (including the quote, if possible).


playful or foolish behavior

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