thirty

American  

[thur-tee] / ˈθɜr ti /

noun

thirties plural

1. a cardinal number, 10 times 3.

2. a symbol for this number, as 30 or XXX.

3. a set of this many persons or things.

4. Printing, Journalism. 30-dash.

5. thirties, the numbers, years, degrees, or the like, from 30 through 39, as in referring to numbered streets, indicating the years of a lifetime or of a century, or referring to degrees of temperature.

   He works in the East Thirties. She must be in her thirties. The temperature was in the thirties yesterday.

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adjective

1. amounting to 30 in number.

thirty British  

/ ˈθɜːtɪ /

noun

1. the cardinal number that is the product of ten and three See also number

2. a numeral, 30, XXX, etc, representing this number

3. (plural) the numbers 30–39, esp the 30th to the 39th year of a person's life or of a century

4. the amount or quantity that is three times as big as ten

5. something representing, represented by, or consisting of 30 units

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determiner

1. 1. amounting to thirty

      thirty trees

   2. ( as pronoun )

      thirty are broken

Usage

Spelling tips for 30 The word thirty (30) is hard to spell because it doesn’t simply combine the spelling of the base number (three) with the suffix -ty, as is done in other easy-to-remember spellings like sixty and seventy.  How to spell thirty: When three is combined with suffixes, it transforms from three (a cardinal number) to third (an ordinal number). Then, the d is dropped: thirteen (not thirdteen); thirty (not thirdty). Remember: there's no d in thirty.

Other Word Forms

Noun Inflected Forms

• thirties
  plural

Etymology

Origin of thirty

before 900; Middle English thritty, Old English thrītig, equivalent to thrī three + -tig -ty ¹; cognate with Dutch dertig, German dreissig, Old Norse thrjātīu

Example Sentences

Thirty percent of all 30-year issuance from blue-chip companies this year has come from hyperscalers versus 13% of year-to-date 10-year supply, Karoui writes.

From Barron's • Jun. 15, 2026

The future of Curry Brand is with Li-Ning,” Curry wrote in a post announcing the deal on his Thirty Ink site.

From Los Angeles Times • Jun. 2, 2026

Thirty homes in Dunmoss View in Coalsnaughton were evacuated as a precaution on Wednesday, a week after 30 homes in the adjacent Benbuck View were told to leave their homes.

From BBC • May 29, 2026

Thirty participants were recruited through the University of Cambridge and the Cambridgeshire and Peterborough NHS Foundation Trust.

From Science Daily • May 28, 2026

Thirty minutes was half of one hour, and half of 25 miles was 12.5.

From "The Lions of Little Rock" by Kristin Levine