thirty

1 of 3

noun (1)

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

thirtieth

2 of 3

adjective

thir·​ti·​eth ˈthər|t|ēə̇th 

ˈthə̄|, 

ˈthəi|, 

|t|, 

|iə̇th

1

: being number 30 in a countable series

the thirtieth day

see Table of Numbers

2

: being one of 30 equal parts into which anything is divisible

a thirtieth share of the money

thirtieth

3 of 3

noun (2)

"

plural -s

1

: number 30 in a countable series

the thirtieth of the month

2

: the quotient of a unit divided by 30 : one of 30 equal parts of anything

one thirtieth of the total

Examples of thirty in a Sentence

Noun (1)

The temperature outside is in the high thirties.

He is in his thirties.

Recent Examples on the Web

Noun

Women in their twenties have healthier eggs, in greater quantities, than women in their thirties. — Anna Russell, New Yorker, 14 Aug. 2026

Cristiano Ronaldo appears twice, both for moves made in his thirties, a testament to his remarkable longevity. — Anantaajith Raghuraman, New York Times, 13 Aug. 2026

In my experience, young talent in their late twenties and early thirties want to be guided and held responsible for meaningful work, not managed at every turn. — M. Todd Abner, Forbes.com, 6 Aug. 2026

Reddit is best known as a forum for discussing how to retire in your thirties, trade conspiracy theories about medical school being a psyop, and gossip about which influencer is taking a GLP-1 but not admitting it. — Marisa Meltzer, Vanity Fair, 4 Aug. 2026

Word History

Etymology

Noun (1)

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

Adjective

Middle English thrittithe, from Old English thrītigotha (akin to Old Norse thrītugandi), from thrītig thirty + -otha, -tha -th

First Known Use

Noun (1)

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