Webster's Revised Unabridged Dictionary · 1913

Decade

Decade , noun

[French décade, Latin decas, -adis, from Greek {not transcribed}, from de`ka ten. See Ten.]

A group or division of ten; esp., a period of ten years; a decennium; as, a decade of years or days; a decade of soldiers; the second decade of Livy.
During this notable decade of years. — Gladstone