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

See Examples For:

thirty thirties

Wood outlined his recommendations in the weekly “Greed and Fear” strategy note he’s been sending to clients for thirty years.

From MarketWatch ● Jul. 10, 2026

The Nikkei 225 gained 38% as the Bank of Japan tightened rates, leading to the highest interest rates in over thirty years.

From Barron's ● Jun. 30, 2026

The phenomenon was observed in Antibes for around thirty minutes.

From Science Daily ● May 21, 2026

Today, thousands of U.S. service personnel, defense officials and their families are stationed in the United Kingdom, as British personnel serve with equal pride across thirty American States.

From The Wall Street Journal ● Apr. 28, 2026

“Ho’mi. See you in thirty minutes. And refill your tea glass. My tea is on social media.”

From "Legendary Frybread Drive-In" by Cynthia Leitich Smith

Confirmed traffic through the strait fell to just 10 ships Monday, according to ship-tracking firm Kpler, compared with levels in the thirties and forties early last week.

From The Wall Street Journal ● Jul. 14, 2026

Ten stories written in as many years, the collection serves as a document of Khong’s thirties, a time when circles shrink and choices narrow.

From Los Angeles Times ● Apr. 13, 2026

African and Russian media identified him as a self-styled "pick-up artist" and online blogger in his thirties who had travelled to Ghana to secretly film his interactions with women.

From BBC ● Feb. 15, 2026

Four men in their thirties, arrested in October and November, are suspected of being the team who conducted the theft on October 19, 2025.

From Barron's ● Jan. 19, 2026

Tonight the temperature is supposed to drop down to the thirties.

From "Blended" by Sharon M. Draper