ENGLISH
REFERENCE

millennium

n.
US //məˈɫɛniəm// UK //mɪlˈɛniəm// mil·len·ni·um
  1. 1 one thousand years (n.)
    B2 Upper Intermediate

    a period of one thousand years.

    a span of time consisting of one thousand years.

    Example

    The ancient castle has stood for nearly a millennium.

    Example

    Archaeologists discovered evidence of a civilization that had thrived for over a millennium before suddenly vanishing from the historical record.

    Usage

    The plural form can be either 'millenniums' or the more formal 'millennia'.

    Teacher's tip

    In academic writing, 'millennia' is the preferred plural form.

    Pitfall
    The millenium was celebrated in 2000.
    The millennium was celebrated in 2000.

    Millennium is frequently misspelled; remember it has a double 'l' and a double 'n'.

  2. 2 the year 2000 (n.)
    B2 Upper Intermediate

    the specific time when one thousand-year period ends and another begins, especially the year 2000.

    the anniversary or transition point marking the end of one thousand-year cycle and the start of the next.

    Example

    Many people were worried about computer errors at the turn of the millennium.

    Example

    The celebrations for the new millennium were marked by spectacular firework displays in major cities across the globe.

    Usage

    Usually used with the definite article 'the'.

  3. 3 an era of peace (n.)
    C2 Proficiency Literary Archaic Religion

    a long period of time in the future when everyone will be happy and peaceful.

    a hoped-for period of joy, serenity, and prosperity; often used in a religious or utopian context.

    Example

    The poet wrote about a coming millennium where war would no longer exist.

    Example

    The philosopher's vision of a secular millennium relied on the triumph of reason over tribalism.

    Teacher's tip

    This sense is rare in modern conversation and is mostly found in older literature or religious texts.
Origin

From Late Latin mīllennium, from Latin mīllennis (“1000-year”) + -ium (forming abstract nouns).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Word family

Last updated June 20, 2026