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1. Occurring every third year.
2. Lasting three years.
1. A third anniversary.
2. A ceremony or celebration occurring every three years.

[From Latin triennis, from triennium, triennium; see triennium.]

tri·en′ni·al·ly adv.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


relating to, lasting for, or occurring every three years
1. a third anniversary
2. a triennial period, thing, or occurrence
[C17: from Latin triennium]
triˈennially adv
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(traɪˈɛn i əl)

1. occurring every three years.
2. lasting three years.
3. a third anniversary.
4. something that appears or occurs every three years.
5. a period of three years; triennium.
tri•en′ni•al•ly, adv.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.triennial - the 300th anniversary (or the celebration of it)
anniversary, day of remembrance - the date on which an event occurred in some previous year (or the celebration of it)
Adj.1.triennial - occurring every third year or lasting 3 years
periodic, periodical - happening or recurring at regular intervals; "the periodic appearance of the seventeen-year locust"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.


[traɪˈenɪəl] ADJtrienal
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005


adj (= lasting 3 years)dreijährig; (= every 3 years)dreijährlich, alle drei Jahre stattfindend
Collins German Dictionary – Complete and Unabridged 7th Edition 2005. © William Collins Sons & Co. Ltd. 1980 © HarperCollins Publishers 1991, 1997, 1999, 2004, 2005, 2007
References in classic literature ?
By another statute, which passed a few years later in the same reign, the term "frequently," which had alluded to the triennial period settled in the time of Charles II, is reduced to a precise meaning, it being expressly enacted that a new parliament shall be called within three years after the termination of the former.
It is recorded that during that triennial agitation no less than twenty-three Circles perished in domestic discord.
All this activity had not caused Ruskin altogether to abandon the teaching of art to the members of the more well-to-do classes, and beginning in 1870 he held for three or four triennial terms the newly-established professorship of Art at Oxford and gave to it much hard labor.
China soon to host global meet on journalism !-- -- PARIS Journalism that usually fits in democracies will come to China in 2022 when the economic giant hosts a triennial global congress of journalism educators.
Nature--Cooper Hewitt Design Triennial, co-organized by Cooper Hewitt, the Smithsonian Design Museum, and Cube design museum in Kerkrade, Netherlands, features over 60 projects to demonstrate how designers are collaborating with scientists, engineers, environmentalists, academics, and other stakeholders to find inventive and promising solutions to the environmental and social challenges confronting humanity today.
Prime Minister Tun Dr Mahathir Mohamad will receive the 'Visionary Leader and Nation Builder' Award at the 20th Asian Association of Management Organisations (AAMO) triennial conference and dinner on April 29.
The Sharjah Triennial will take place across several prominent sites of the emirate.
TODAY (FRIDAY) Preview - Visual arts / Asia Triennial Manchester 2018 At a time when national identity is becoming increasingly difficult to define, the latest edition of the Asia Triennial Manchester - Europe's only triennial dedicated to visual art on the theme of Asia - is aiming to bring some much-needed clarity to the discussion.
RAFI's Triennial Awards recognize individuals and / or groups committed to building a more humane, equitable and caring society, individuals and groups that touch other peoples' lives, bring about change to improve the conditions of the less privileged.
At another Florida reactor, this one in Citrus County, a Triennial Fire Protection Baseline Inspection in July 2002 discovered, according to a "Briefing Summary," that not only did the Crystal River plant use "a significant number of local manual actions" instead of automatic shutdown, but that the plant's fire plan neglected to give adequate consideration to some of the practical difficulties of shutting a nuclear power plant down by hand.
July 24-28 2005 Brisbane, Queensland Australia 27th Triennial Congress International Confederation of Midwives