The term 'LO-O-ONG TIME' can be broken down into two crossword solutions: EON (3 letters) and EONS (4 letters). An EON is an immeasurably long period of time, often used to describe the age of the universe or the Earth. EONS are divided into eras, periods, and epochs. EONS are the longest division of geological time and are typically hundreds of millions of years in length. EONS are also used to describe a very long period of time, such as an eternity.