An eternity is a very long period of time, often used to refer to an infinite amount of time. The term can be broken down into four crossword solutions: EONS (4 letters), AEON (4 letters), AGES (4 letters), and EON (3 letters). EONS refers to a very long period of time, usually millions of years. AEON is another word for an eternity, while AGES is a much longer period of time than a single lifetime. Finally, EON is the shortest of the four terms, referring to a period of one billion years.