Something that happens every three years is a triennialevent.
A triennial event happens every three years.
Sextennial means "Recurring every six years."
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~ this means twice in one yearbiennial~ this means once every two years
Biennial or biannual can refer to something which happens every two years.
The word is triennial.
tri-annual
The word for every 75 years is "septuagesimal."
The word for every twenty years is "score."
A triennial event happens every three years.
The word Biennial means Every two years
Quadrennial
Every three years
An event that occurs once every three years.
Every decade
Sextennial means "Recurring every six years."
The word is Triennial.