Meaning of TRIENNIAL in English

I. (ˈ)trī|enēəl, -nyəl adjective

Etymology: Latin trienni um period of three years (from tri- + -ennium, from annus year) + English -al — more at annual

1. : continuing or having a term of three years

a triennial reign

a triennial parliament

2. : occurring, appearing, or being made, done, or acted upon every three years

a triennial election

II. noun

( -s )

Etymology: Latin trienni um + English -al, n. suffix

: a triennial event, appearance, or occasion: as

a. : a triennial episcopal visitation in the Church of England

b. : a third anniversary

c. : something (as a serial publication) that appears every three years

Webster's New International English Dictionary.      Новый международный словарь английского языка Webster.