noun \mə-ˈle-nē-əm\

: a period of 1,000 years

: a period of a thousand years counted from the beginning of the Christian era

plural -nia \-nē-ə\ or mil·len·niums

Full Definition of MILLENNIUM

a :  the thousand years mentioned in Revelation 20 during which holiness is to prevail and Christ is to reign on earth
b :  a period of great happiness or human perfection
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

Examples of MILLENNIUM

  1. The book describes the changes that have occurred in the landscape over many millennia.
  2. The year 2000 was celebrated as the beginning of the third millennium.


New Latin, from Latin mille thousand + New Latin -ennium (as in biennium)
First Known Use: circa 1638

Other Calendar Terms

antedate, estival, gloaming, luster, sesquicentennial

Rhymes with MILLENNIUM


noun    (Concise Encyclopedia)

Period of 1,000 years. The Gregorian calendar, put forth in 1582 and subsequently adopted by most countries, did not include a year 0 in the transition from BC (years before Christ) to AD (those since his birth). Thus, the 1st millennium is defined as spanning years 1–1000 and the 2nd years 1001–2000. Although numerous popular celebrations marked the start of the year 2000, the 21st century and 3rd millennium AD began on Jan. 1, 2001.


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