[trahy-en-ee-uh l]
See more synonyms for triennial on
  1. a third anniversary.
  2. something that appears or occurs every three years.
  3. a period of three years; triennium.

Origin of triennial

First recorded in 1555–65; trienni(um) + -al1
Related formstri·en·ni·al·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for triennial

triennial, tertiary, tertian

Examples from the Web for triennial

Contemporary Examples of triennial

Historical Examples of triennial

British Dictionary definitions for triennial


  1. relating to, lasting for, or occurring every three years
  1. a third anniversary
  2. a triennial period, thing, or occurrence
Derived Formstriennially, adverb

Word Origin for triennial

C17: from Latin triennium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for triennial

1630s, "lasting three years;" 1640s, "occurring every three years," from Latin triennium "three-year period," from tri- "three" (see tri-) + annus "year" (see annual). For vowel change, see biennial.

Online Etymology Dictionary, © 2010 Douglas Harper