sev·en·ty 
(sĕvən-tē)
(sĕvən-tē)n.
1. The cardinal number equal to 7 × 10.
2. seventies
a. A decade or the numbers from 70 to 79: They became grandparents in their seventies. The temperature hovered in the seventies.
b. often Seventies The decade from 70 to 79 in a century.
[Middle English, from Old English -seofontig (in hundseofontig, the decade seventy, seventy); see sept in the Appendix of Indo-European roots.]
seven·ty adj. & pron.