thirty

noun

thir·​ty ˈthər-tē 

plural thirties

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

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 demand for fertility treatment is also rising as more couples are delaying parenthood until their thirties or forties. —Michelle Travis, Forbes.com, 26 Mar. 2025

The premise is simple: Doute and the Cartwright-Taylors have left West Hollywood and SUR behind for the Valley, in the hopes of living a more domestic life alongside a bunch of their friends in their thirties and forties—most of whom are married with kids. —Naomi Fry, The New Yorker, 13 Mar. 2025

Though many proponents of the social turn are experienced analysts—both Holmes and Moss were in their seventies—the approach is particularly attractive to younger clinicians as well as to current analysts in training, who tend to be in their thirties or forties. —Maggie Doherty, Harper's Magazine, 28 Feb. 2025

Last year, Jasmine Paolini made two Grand Slam finals for the first time, at the age of twenty-nine, and one of the game’s top Americans, Jessica Pegula, found her most consistent success in her late twenties and early thirties. —Louisa Thomas, The New Yorker, 9 Mar. 2025

Word History

Etymology

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

First Known Use

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

Phrases Containing thirty

• thirty-eight
• thirty-second note
• thirty-second rest
• thirty-thirty
• thirty-three
• thirty-two
• thirty-twomo

Rhymes for thirty

• birdie
• gurdy
• purdy
• sturdy
• wordy

Kids Definition

thirty

noun

thir·​ty ˈthərt-ē 

plural thirties

1

: a number equal to three times 10 see number

2

plural : the numbers 30 to 39

especially : the years 30 to 39 in a lifetime or century

thirtieth

-ē-əth 

noun or adjective

thirty adjective or pronoun