thir·ty 
(thûrtē)
(thûrtē)n. pl. thir·ties
1. The cardinal number equal to 3 × 10.
2. thirties
a. A decade or the numbers from 30 to 39: They settled down in their thirties. The temperature fell into the thirties.
b. often Thirties The decade from 30 to 39 in a century.
3. An indication of the end of a news story, usually written 30.
4. Sports The second point that is scored by one side in tennis.
[Middle English thritty, thirty, from Old English thrītig; see trei- in the Appendix of Indo-European roots.]
thirty adj. & pron.
- Indo-European root: bhrū-
- Indo-European root: bhā-
- Indo-European root: bhā-
- Indo-European root: bhāghu-
- Indo-European root: bhāgo-
- Indo-European root: dail-
- Indo-European root: daiwer-
- Indo-European root: dakru-
- Indo-European root: de-
- Indo-European root: deik-
- Indo-European root: dek-
- Indo-European root: dekm̥
- Indo-European root: deks-
- Indo-European root: del-
- Indo-European root: del-
- Indo-European root: dem-
- Indo-European root: demə-
- Indo-European root: dent-
- Indo-European root: der-
- Indo-European root: derk-
- Indo-European root: deru-
- Indo-European root: deu-
- Indo-European root: deu-
- Indo-European root: deuk-
- Indo-European root: deuə-