The term 'many years' can be represented by several different words in a crossword puzzle, including 'EONS' (4 letters), 'AGE' (3 letters), 'AGO' (3 letters), 'EON' (3 letters), 'AEON' (4 letters), 'AGES' (4 letters), and 'DECADES' (7 letters). EONS are the longest unit of geological time, and are usually divided into eras. An AGE is a period of time in history or prehistory, and AGO is used to refer to a period of time that has passed. An EON is an indefinite and very long period of time, while an AEON is an indefinitely long period of time that is often associated with eternity. AGES is a plural form of AGE, and DECADES are periods of 10 years.