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

All the hunters were in their mid-thirties to mid-forties. —Tim Kelly, Outdoor Life, 4 Sep. 2025

The twentysomethings are now in their thirties and this first feature has a weightier tone tackling issues of parenthood, economic survival and migration, albeit with love and laughter. —Melanie Goodfellow, Deadline, 2 Sep. 2025

At least four settlers on the Galápagos island of Floreana vanished or died in the early nineteen-thirties, under circumstances that were contested long afterward among some of the survivors. —Justin Chang, New Yorker, 26 Aug. 2025

Those displays earned Salah a new two-year contract — despite Liverpool owners Fenway Sports Group’s reluctance to hand out large deals of over 12 months to players in their thirties — and the unstinting respect of his peers. —Sarah Shephard, New York Times, 20 Aug. 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