WORD ROOTS: ANN, ENN

millennium

the 1000th anniversary (or the celebration of it)

anniversary

the date on which an event occurred in some previous year (or the celebration of it)

superannuated

too old to be useful

semiannual

twice a year

annual

yearly

annals

historical records

perennial

lasting for a long time

centennial

n. A 100th anniversary or its celebration

biannual

occurring twice a year

annuity

payment received every year