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

Morris Kiruga, the writer and journalist behind the exposé, is a good-humored man in his mid-thirties who trained as a forensic scientist. —Hettie O'Brien, The Dial, 21 Apr. 2026

Heal, who is fifty, only became a serious Catholic in his late thirties, and had spent the first part of his career as a firefighter in Arizona. —Emma Green, New Yorker, 17 Apr. 2026

Interest after the Gaza war skewed toward people in their twenties and thirties. —Jacqueline Munis, Fortune, 16 Apr. 2026

Pinell’s second film after Kiss and Cry, Shana stars her regular collaborator Éva Huault as a woman in her thirties navigating dead-end jobs, drug deals and an impossible relationship with a toxic thug, Moïse. —Melanie Goodfellow, Deadline, 14 Apr. 2026

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