Millenium

Millennium is a noun that denotes a period of 1,000 years. The word derives from Latin mille- meaning thousand and annus meaning year. In historical chronology it is used to label large eras, such as the second millennium AD, which roughly covers the years 1000 to 1999 or 1001 to 2000 depending on counting convention. In religious contexts, millennialism refers to beliefs about a future 1,000-year reign on earth, with several interpretive viewpoints within Christianity.

Spelling note: The standard spelling is millennium with two n’s. The form millenium is a common misspelling and is typically flagged as incorrect in formal writing, though it appears in some brand names and older texts.

Beyond chronology and theology, millennium is used more generally to describe any 1,000-year period. The term also appears in discussions of long-term planning, archaeology, and historiography, where clear boundaries between millennia and centuries may vary by convention.