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

While Fleming’s early works place Bond at being somewhere between his late twenties and early thirties, First Light’s version is 26, but looks downright baby-faced. —Christopher Cruz, Rolling Stone, 18 June 2025

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, 10 June 2025

Typically, weightlifters can be in their prime into their late twenties and thirties. —Andy Frye, Forbes.com, 10 June 2025

The undercover cop on the subway platform was in his early thirties, McCullough guessed, and evidently humorless, or, more likely, fulfilling a quota. —Ben McGrath, New Yorker, 2 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