ninety

American  

[nahyn-tee] / ˈnaɪn ti /

noun

plural

nineties

1. a cardinal number, ten times nine.

2. a symbol for this number, as 90 or XC.

3. a set of this many persons or things.

4. nineties, the numbers, years, degrees, or the like, from 90 through 99, as in referring to numbered streets, indicating the years of a lifetime or of a century, or degrees of temperature.

   His grandmother is in her nineties.

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adjective

1. amounting to 90 in number.

ninety British  

/ ˈnaɪntɪ /

noun

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

2. a numeral, 90, XC, etc, representing this number

3. something represented by, representing, or consisting of 90 units

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determiner

1. 1. amounting to ninety

      ninety times out of a hundred

   2. ( as pronoun )

      at least ninety are thought to be missing

Usage

Spelling tips for 90 The word ninety (90) is hard to spell because it can be hard to remember whether to include the e from nine when combining it with the suffix -ty. How to spell ninety: To spell ninety, you simply combine the base number (nine) with the suffix -ty, which means "multiple of 10." 9 x 10 = 90 or, in writing, nine + -ty = ninety.

Etymology

Origin of ninety

before 1000; Middle English nineti, Old English nigontig. See nine, -ty ¹

Example Sentences

And those improved recommendations come at a much lower cost, he said, sometimes ninety percent less than using the proprietary models favoured by US AI developers.

From BBC • Jan. 23, 2026

“Seventy to ninety percent of my life throughout those years was with him,” he says.

From Los Angeles Times • Sep. 10, 2025

After ninety days, there were four times fewer people in the benralizumab group that failed treatment compared to standard of care with prednisolone.

From Science Daily • Nov. 27, 2024

In 1968, four years after the nursery study began at Howard, the federal Children’s Bureau released a ninety two-page report of the findings.

From Scientific American • Oct. 26, 2023

Aunt Florentine had ordered her headstone the year she turned ninety.

From Each Little Bird That Sings by Deborah Wiles