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."
Biennial or biannual can refer to something which happens every two years.
Something that happens every six years is sexennial.
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.
Quadrennial
The word Biennial means Every two years
Every three years
An event that occurs once every three years.
Every decade
Sextennial means "Recurring every six years."
Sextennial means "Recurring every six years."