nine·ty 
(nīntē)
(nīntē)n. pl. nine·ties
1. The cardinal number equal to 9 × 10.
2. nineties
a. 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.
b. often Nineties The decade from 90 to 99 in a century.
[Middle English ninti, from Old English nigontig; see new in the Appendix of Indo-European roots.]
ninety adj. & pron.
- Indo-European root: kau-
- Indo-European root: kaə-id-
- Indo-European root: ked-
- Indo-European root: keg-
- Indo-European root: kei-
- Indo-European root: keiə-
- Indo-European root: kekw-
- Indo-European root: kel-
- Indo-European root: kel-
- Indo-European root: kelə-
- Indo-European root: kelə-
- Indo-European root: ken-
- Indo-European root: kenk-
- Indo-European root: kens-
- Indo-European root: kent-
- Indo-European root: ker-
- Indo-European root: ker-
- Indo-European root: ker-
- Indo-European root: kerd-
- Indo-European root: kerp-
- Indo-European root: kers-
- Indo-European root: kerə-
- Indo-European root: kes-
- Indo-European root: keuə-
- Indo-European root: klei-