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

Your 20s and 30s are for learning skills Using Obama’s mantra for career success, Raman advises those in their twenties and early thirties to forgo titles completely to focus on skills development, before specializing in their mid-thirties. —Orianna Rosa Royle, Fortune, 18 Mar. 2024

Most of them had been built in the thirties, which was not long after the area had been known as the Outside Lands—desolate and windswept, just scattered people growing vegetables in the shifting dunes. —Zach Williams, The New Yorker, 18 Mar. 2024

Born in San Francisco, Ruiz came to Sacramento by way of Miami in his thirties. —Cathie Anderson, Sacramento Bee, 29 Feb. 2024

All of these artists were part of the Harlem Renaissance, in the nineteen-twenties and thirties, an explosion of innovation in the arts which established Harlem as the creative center of Black culture. —Calvin Tomkins, The New Yorker, 5 Feb. 2024

Compound interest helps explain how average net worth reaches $500,000 for people in their late thirties. —USA TODAY, 14 Jan. 2024

The second-most expensive Magnificent Seven stock is Nvidia Corp. at around 36 times forward earnings, while the rest trade between the low twenties and low thirties. —Esha Day, Fortune, 11 Feb. 2024

Production of the collagen that keeps the skin plump and firm begins to dwindle in our late twenties and early thirties, but a thoughtful daily routine can help with retaining and boosting it—without resorting to the needle. —Ana Morales, Vogue, 10 Feb. 2024

Among the loudest evangelists was a naturopath named Paul C. Bragg, who, in the nineteen-twenties and thirties in Los Angeles, became a wellness adviser to the stars and then to the broader public. —Hannah Goldfield, The New Yorker, 5 Feb. 2024

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-second note
• thirty-second rest
• thirty-two
• thirty-three
• thirty-thirty
• thirty-twomo
• thirty-eight

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