Definition of thirty in English:

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Pronunciation: /ˈTHərdē/

cardinal number (plural thirties)

1The number equivalent to the product of three and ten; ten less than forty; 30: thirty or forty years ago thirty were hurt thirty of her school friends (Roman numeral: xxx, XXX)
More example sentences
  • He had no devoted readership and little chance of remaining in print for long, let alone being republished in thirty or forty years' time.
  • He is apt to spend thirty or forty pages on an incident to which an equally good writer might devote three.
  • But there is no doubt in my mind that people were happier thirty or forty years ago.
1.1 (thirties) The numbers from thirty to thirty-nine, especially the years of a century or of a person’s life: a woman in her thirties she was a famous actress in the thirties
More example sentences
  • Yeah, this record is kind of about what happens when you let your adolescence continue into your thirties.
  • These are people who grew up in Ireland in the twenties and thirties and reached maturity in the era of World War Two.
  • The woman was described as being aged in her thirties, with mousy brown hair cut in a bowl style and a spotty complexion.
1.2Thirty years old: I’ve got a long way to go before I’m thirty
More example sentences
  • Parents over the age of thirty are becoming a larger proportion of first-time parents.
  • I put it behind the desk as requested and followed the doctor, a woman roughly around the age of thirty.
  • It is a young population, with the majority under the age of thirty.
1.3Thirty miles an hour: doing about thirty



Pronunciation: /ˈTHərdēəTH/
ordinal number
Example sentences
  • Jordan is completing his thirtieth year of service with the Army's 35th Signal Brigade and reaching his mandatory retirement date.
  • Ranking above Bulgaria were Slovenia, in fourteenth place, Poland in thirtieth place, and Croatia in thirty-third place.
  • The commemorative statue was unveiled on the thirtieth anniversary, in January this year.


Pronunciation: /ˈTHərdēˌfōld/
adjective& adverb
Example sentences
  • Since then, transfer fees have multiplied thirtyfold.
  • When the ice melted, which it did quickly, the sudden reduction in weight caused a thirtyfold increase in volcanic activity, creating the numerous volcanic mountains that now dominate the landscape.
  • A thousandfold increase in the computer time invested in the task has brought a thirtyfold improvement in precision.


Old English thrītig (see three, -ty2). The spelling with initial thi- is recorded in the 15th century, and has been the prevalent form since the 16th century.

Words that rhyme with thirty

Alberti, Bertie, dirty, flirty, shirty

For editors and proofreaders

Syllabification: thir·ty

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