mil·len·ni·um 
/məˈlɛnijəm/ noun
plural mil·len·nia /məˈlɛnijəm/ noun /-nijə/ or mil·len·ni·ums [count] 1 : a period of 1,000 years
▪ The book describes the changes that have occurred in the landscape over many millennia. 2 : a period of a thousand years counted from the beginning of the Christian era
▪ The year 2000 was celebrated as the beginning of the third millennium. ▪ We had a party to celebrate the millennium. [=the beginning of the millennium]
▪ The book describes the changes that have occurred in the landscape over many millennia.
▪ The year 2000 was celebrated as the beginning of the third millennium. ▪ We had a party to celebrate the millennium. [=the beginning of the millennium]
— mil·len·ni·al /məˈlɛnijəl/ adjective
▪ millennial celebrations
/məˈlɛnijəl/ adjective ▪ millennial celebrations
