[ee-uh
n, ee-on] 
| 1. | an indefinitely long period of time; age. |
| 2. | the largest division of geologic time, comprising two or more eras. |
| 3. | Astronomy. one billion years. |
| e·on also ae·on (ē'ŏn', ē'ən) n.
[Late Latin aeōn, from Greek aiōn; see aiw- in Indo-European roots.] |
