[dict]semiannual[SEMI] happening every half of a year (that is, every six months)
[dict]centennial[CENT] the one hundred year anniversary
[dict]millennium[MILL] a period of one thousand years
Level Two
[dict]annals a record of what has happened through the years
[dict]anno Domini[DOMIN] literally, “in the year of the Lord,” A.D.; the number of years since the birth of Christ (anno is the ablative case of annus.)
[dict]annuity an investment that provides yearly dividends
[dict]biennial[BI] happening every two years. (Some people will use this to mean “twice in a year,” but semiannual is to be preferred.)
[dict]perennial[PER] continuing through the years; lasting, enduring