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

From behind sunglasses and baseball caps, members appear to be in their mid-twenties to early thirties. —Lina Abascal, Los Angeles Times, 7 May 2025

Herb Baumeister, a businessman and father of three, is believed to have killed at least 25 men—primarily gay men in their twenties and thirties—between the mid-1980s and 1996. —Jenna Dejong, MSNBC Newsweek, 30 Apr. 2025

When people can only make it to their early thirties, what’s the point of having kids? —George Yang, Rolling Stone, 23 Apr. 2025

And my grandparents and my great grandparents and cousins and aunts and everything, from the thirties and the twenties and the forties. —Mike Fleming Jr, Deadline, 21 Apr. 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