Save Gender Feminine & Masculine Usage English Pronounced Pron. [mɪ.ˈlɛn.ɪ.əm] [key·simplify] Other Forms FormsMillenium Meaning & History From the word referring to a period of time spanning a thousand years, from a Latin combination of mīlle meaning "thousand" and annus meaning "year" (with a>e vowel change and addition of abstract noun suffix -ium).