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 golden mahseer and goonch catfish are some of the thirty flagship fish species which have now been prioritised for global conservation by the UN in a new report.

From BBC ● Mar. 24, 2026

The team analyzed the activity of hundreds of genes in about thirty cell clones taken from two primary colon tumors.

From Science Daily ● Mar. 21, 2026

Irian erupted to the surface, thirty feet from the boat.

From "Impossible Creatures" by Katherine Rundell

It was towards the end of last year that a woman in her late thirties walked into a Glasgow police station to report a crime.

From BBC ● Jul. 23, 2026

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

"They'll have to take us by force," said the man in his thirties, who fled his home with his wife and two-year-old son, insisting they "will not surrender".

From Barron's ● Mar. 25, 2026

But soon he was back in the thirties and was searching the radio, listening for speeches from FDR.

From "Middlesex: A Novel" by Jeffrey Eugenides