nounWord forms: plural-lenniums or -lennia (-ˈleniə)
1.
a period of two thousand years
2.
a two thousandth anniversary
Also: bimillenary, bimillennial
Word origin
[bi-1 + millennium]bi- is a combining form meaning “twice,” “two,” used in the formation of compound words.Other words that use the affix bi- include: biceps, bilabial, bilateral, bilingual, bivalent