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

Fellig began freelancing for the tabloid press in his thirties. —Naomi Fry, The New Yorker, 22 Feb. 2025

Search for your county here: By age group The majority of unmarried people are in their early twenties to thirties, with an increase among those in their mid-sixties too. —Taylor Johnston, CBS News, 14 Feb. 2025

Some even had a policy, restricting them to only offering one-year contract extensions to players in their thirties (something Real Madrid still mostly do). —Sarah Shephard, The Athletic, 11 Feb. 2025

Per the study, the percentage of female characters plummeted from 35 percent in their thirties to 16 percent in their forties. —Kate Erbland, IndieWire, 11 Feb. 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