The term 'thousands of years' can be represented by four different words: EON (3 letters), EONS (4 letters), AEON (4 letters), and MILLENNIA (9 letters). An EON is the longest division of geological time, lasting hundreds of millions of years. EONS are divided into eras, which are further divided into periods, epochs, and ages. An AEON is an indefinite period of time, often used to refer to a very long period of time. A millennium is a period of one thousand years.