decade

noun

1. a group of ten
2. a period of ten years; esp., in the Gregorian calendar
   1. officially a ten-year period beginning with the year 1, as 1921-1930, 1931-1940, etc.
   2. in common usage, a ten-year period beginning with a year 0, as 1920-1929, 1930-1939, etc.
3. a division of the rosary consisting of one large bead and ten small beads

Origin: LME < OFr < LL decas (gen. decadis) < Gr dekas < deka, ten