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 an effort to overcome grief and find herself again, Hollis gets the idea to host a weekend away at her house on Nantucket with three friends from different stages in her life: her childhood, her twenties, thirties, and one surprise fifth star. —Joe Otterson, Variety, 2 July 2025

Solo treks through his native Scotland during the height of his struggles, his thirties, provided rare solace from stress, trauma, and depression. —Stephanie Vermillion, Outside Online, 1 July 2025

In his early thirties, Abu Shabab is from a prominent Bedouin family in southern Gaza. —Tim Lister, CNN Money, 8 June 2025

Back in the thirties, people thought nuclear power was going to revolutionize the world in a good way. —Mike Fleming Jr, Deadline, 27 June 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