nothing
A triennial event happens every three years.
Something that happens every six years is sexennial.
It is a triennial event. A triennial event happens three times a year.
bidecadal
Semicentennial
An event occurring every two years is referred to as a biennial event. This pattern indicates that the event happens once every two years.
True.
Chicago Cubs in the World Series?
Leap year
I think you are asking about a census.
Every 100 years is called a century, made up of 10 decades.
the word is novennial....