Triennial means three years-- 36 months.
Triannual means: occurring three times per year. How's that for unambiguous? Triannual doesn't really imply that the event described must happen exactly every 4 months-- only that it happens three times during a year.
we should have celebrated the triennial anniversary of our runnig race at our high school.
There is disagreement on whether there even exists a proper, unambiguous term for "every four months." Many use triannualfor the purpose. There is some logic to this, since biannualmeans twice yearly, whereas biennial means every two years, and triennial means every three years. But some dictionaries, ones that do list triannual, list it as a synonym for triennial ("every three years") while at the same time giving it the meaning of "three times yearly" And although biennial and biannual are well defined, they are often confused in usage. And in horticulture, biannualrefers to a two-year cycle. Some have suggested the awkward term quadrimonthly, while others suggest the straightforward thrice-yearly. But whatever we do we have to be clear. Even the writers who use triannual often attach the definition alongside it, because they know it can be misunderstood.
The following months have 1 syllable:MarchMayJune
Two moons usually means two months. The moon becomes full once per month (generally, or in rule of thumb terms)
FDB
Triennial Convention was created in 1814.
we should have celebrated the triennial anniversary of our runnig race at our high school.
The triennial festival was coming to town this year, as it did three years ago.
Echigo-Tsumari Art Triennial was created in 2003.
It is a triennial event. A triennial event happens three times a year.
Centennial
triennial
'triennial'
QUADENNIAL
The word is Triennial.
Triennial
tertian, tertiary, triennial, second to last