The word "millennium" refers to a period of one thousand years. It's often used to describe a significant time span in history, such as the first millennium (1 AD to 1000 AD) or the second millennium (1001 AD to 2000 AD). In a broader sense, it can also signify the year 2000, which was a point of great cultural and technological significance as people celebrated the new century.
The term "millennium" comes from the Latin word "mille," meaning "thousand," combined with the suffix "-ennium," which denotes a period of years. Thus, it literally translates to "a thousand years."