What is the name for 1000000000 years? Some terms referenced do have year values assigned to them (Epoch at 1,000,000 years and Aeon at 1,000,000,000 years) but common usage relates to geological time periods which are not consistent in length.
Why is millennium not a million? The words million and millennium are formed differently and so mean different things. Millennium is a Latinate compound of mill- meaning “thousand” and -ennium, meaning “year”. (Compare related compounds such as biennium or centennial). Its meaning follows straightforwardly from its composition.
What is longer than a millennium? Eon: The longest amount of time. Era: Several eras make up an eon. Period: Several periods make up an era. Epoch: Several epochs make up a period.
What is 5 decades called? quinquennially kwin-ˈkwe-nē-ə-lē , kwiŋ- adverb.