millennium

noun

mil·​len·​ni·​um mə-ˈle-nē-əm 

plural millennia mə-ˈle-nē-ə  or millenniums

1

a

: the thousand years mentioned in Revelation (see revelation sense 3) 20 during which holiness is to prevail and Christ is to reign on earth

b

: a period of great happiness or human perfection

2

a

: a period of 1000 years

especially : one reckoned from the beginning of the Christian era

at the start of the third millennium

b

: a 1000th anniversary or its celebration

In 2015 the city of Leipzig, Germany, celebrated its millennium.

Did you know?

Since in Latin mille means "thousand", a millennium lasts 1,000 years. Thus, we're living today at the beginning of the third millennium since the birth of Christ. But some religious sects, relying on a prophecy in the biblical Book of Revelation, speak of a coming millennium when Jesus will return to reign on earth for 1,000 years, evil will be banished, and all will live in peace and happiness. Members of these sects who keep themselves in a constant state of preparedness are called millenarians or millennialists.

Examples of millennium in a Sentence

The book describes the changes that have occurred in the landscape over many millennia.

The year 2000 was celebrated as the beginning of the third millennium.

Recent Examples on the Web

By growing slowly in hostile environments, these trees outlive their peers by millennia. —Scott Travers, Forbes.com, 27 Apr. 2025

But the sources of silk, the silkworm cocoons and the silkworms themselves, have remained incredibly consistent — a result of many millennia of B. mori cultivation. —Amy Paturel, Discover Magazine, 22 Apr. 2025

Few of us have beheld a living wonder than the revival of Catholic-Jewish collaboration from nearly two millennia of death and destruction. —Joshua Stanton, New York Daily News, 20 Apr. 2025

The Dacians settled in present-day Romania in the 1st millennium B.C. —Andrea Margolis, FOXNews.com, 15 Apr. 2025

Word History

Etymology

New Latin, from Latin mille thousand + New Latin -ennium (as in biennium)

First Known Use

circa 1638, in the meaning defined at sense 1a

Phrases Containing millennium

• the millennium

Rhymes for millennium

• biennium
• quinquennium
• triennium

Kids Definition

millennium

noun

mil·​len·​ni·​um mə-ˈlen-ē-əm 

plural millennia

-ē-ə

or millenniums

1

a

: a period of 1000 years

b

: a 1000th anniversary or its celebration

2

: a period of great happiness

millennial

-ē-əl

adjective