/dek"ayd/ ; Brit. also /deuh kayd"/ , n.
1. a period of ten years: the three decades from 1776 to 1806.
2. a period of ten years beginning with a year whose last digit is zero: the decade of the 1980s.
3. a group, set, or series of ten.
[ 1425-75; late ME decad- (s. of decas ) dekad- (s. of dekás ) group of ten, equiv. to dék ( a ) TEN + -ad- -ADE 2 ]