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

In my experience, young talent in their late twenties and early thirties want to be guided and held responsible for meaningful work, not managed at every turn. — M. Todd Abner, Forbes.com, 6 Aug. 2026

Reddit is best known as a forum for discussing how to retire in your thirties, trade conspiracy theories about medical school being a psyop, and gossip about which influencer is taking a GLP-1 but not admitting it. — Marisa Meltzer, Vanity Fair, 4 Aug. 2026

One of the most brutal is led by Bello Turji, a Fulani man believed to be in his early thirties. — Alexis Okeowo, New Yorker, 3 Aug. 2026

For Winfrey, that professional reassurance came from a decade of hard work following her big break in her thirties. — Emma Burleigh, Fortune, 27 July 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