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

Binge drinking, which increases the risk of breast and several other types of cancers, is also becoming more common among women in their thirties and forties, Siegel notes. —Lisa Rapaport, EverydayHealth.com, 21 Jan. 2025

The book features a hostess named Dolly Harrison, her first name probably an homage to both Dolley Madison and Dolly Gann, a Washington hostess of the twenties and thirties. —Thomas Mallon, The New Yorker, 20 Jan. 2025

According to the report, women are most likely to consider starting a social enterprise in their twenties and early thirties, but there is a distinct drop off in the middle years, with the low point identified as 38.6. —Trevor Clawson, Forbes, 19 Jan. 2025

As mentioned above, Doughty is still good for 50 points even well into his thirties, and a lot of that is via his prowess on the power play. —Yaakov Katz, Newsweek, 17 Jan. 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

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