bidecadal
True.
Every 100 years is called a century, made up of 10 decades.
A false rumor is floating around the Internet that this happens only once every 823 years. The reality is that it happens whenever the first day of October is on Friday, which happens on average once every seven years. The last time for this "rare" event was 6 years ago, back in 2004. And the time before that was 5 years previously, in 1999.
Every 200 years
You have the world cup, the U.S president is elected, the Olympics are held , and so is the Euro cup. This all happens every four years.
A triennial event happens every three years.
It is a triennial event. A triennial event happens three times a year.
Something that happens every six years is sexennial.
Quadrenial
nothing
Semicentennial
I think you are asking about a census.
Chicago Cubs in the World Series?
Leap year
True.
Every 100 years is called a century, made up of 10 decades.
the word is novennial....