Ninety definition

nīntē
Frequency:
The cardinal number equal to 9 × 10.
noun
10
3
Nine times ten.
adjective
8
1
The cardinal number between eighty-nine and ninety-one; 90; XC (or LXXXX)
noun
5
3
A decade or the numbers from 90 to 99.

My grandparents are in their nineties. During the heat wave, the temperature stayed in the nineties.

noun
0
1
The decade from 90 to 99 in a century.
noun
0
1
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the Gay Nineties
  • the decade 1890-99 in the U.S.
idiom
2
2
the nineties
  • the numbers or years, as of a century, from ninety through ninety-nine
idiom
3
1

Other Word Forms

Noun

Singular:
ninety
Plural:
nineties

Idioms and Phrasal Verbs

the Gay Nineties
the nineties

Origin of ninety

  • Middle English ninti from Old English nigontig newn̥ in Indo-European roots

    From American Heritage Dictionary of the English Language, 5th Edition