Plural of millennium

irregular plural

The plural of millennium is millennia or millenniums.

Forms of millennium

But these seekers, too, are saved - by virtue of the inherited symbolic aids of society, the rites of passage, the grace-yielding sacraments, given to mankind of old by the redeemers and handed down through millenniums.1968, Joseph Campbell, The Hero with a Thousand Faces, 2nd edition, London: Fontana Press, published 1993, page 23
How this happens no one really knows, despite the efforts of philosophers and psychologists over two and a half millennia to study the phenomenon.1972, Mortimer J. Adler, Charles Van Doren, How to Read a Book, →ISBN, →LCCN, page 25
The eventual regrowth of the forest to its primeval state will take centuries, if not millennia.From the entry regrowth
Linen has made cool and breathable clothing for millennia.From the entry cool
A cosmopoietic event occurred many millennia ago.From the entry cosmopoietic

noun A period of time consisting of one thousand years.
noun The year in which one period of one thousand years ends and another begins, especially the year 2000.
noun Any long (and possibly endless) era of universal happiness, peace, and prosperity, predicted by various people to come about someday.

What is the plural of millennium?: The plural of millennium is millennia or millenniums.
Which is correct, millennia or millenniums?: Both are used. millennia is the more common of the two in English writing.
Is millennium countable?: Millennium is a countable noun.

Adapted from Wiktionary: millennium (page history and authors) and the entries of its forms. Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws left out forms marked obsolete, archaic, rare or dialectal and added the examples. Wiktionary data of 2026-09-02.

Last updated: 2026-09-02

Cite this page: “Plural of millennium.” Word.ws, https://word.ws/plural/millennium. Based on Wiktionary, CC BY-SA 4.0.