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

This underdog story chronicles their early days and the breakout movies that secured their legacies when each was still in his thirties. —The New Yorker, New Yorker, 2 Mar. 2026

Officers responded and found a woman in her thirties with injuries to her face, as well as blood around several areas inside of a small apartment. —Phillip Molnar, San Diego Union-Tribune, 28 Feb. 2026

In February my wife Linda lost her sister Frankie to melanoma in her early thirties. —Rick Davis, CNN Money, 27 Feb. 2026

Winds associated with the low-pressure system of the storm may keep kids indoors for much of today, but temperatures in the thirties in the next couple of days will mean more opportunities for kids to play in the white stuff. —Stephanie Pappas, Scientific American, 23 Feb. 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