Triennial, from Latin "triennium".
Triennial
The word is... bicentennial.
Consecutive.
Every decade
A century means one hundred consecutive years, and adjective form is centennial. The adverb form centennially is rarely used.
enneatical
Biennial means "occurring every two years," OR "lasting for two years." The word biannual can also mean "occurring every two years," although its most common meaning is "occurring twice a year."
Biannual. Biannual can mean occurring every two years, OR occurring twice a year. Biennial, on the other hand, means only the former: occurring every two years.
Triennial
annual or anniversary
No, "biannual" is not hyphenated. It is a single word that means occurring twice a year. However, it is important to distinguish it from "biennial," which means occurring every two years. Always use "biannual" without a hyphen when referring to events that happen semiannually.
The word Biennial means Every two years
Sextennial means "Recurring every six years."
Biannual~ this means twice in one yearbiennial~ this means once every two years
The word is "millennium".
Sextennial means "Recurring every six years."
biennial