[ 'i:ən ]
■ noun ( US or technical also eon )
1》 an indefinite and very long period.
2》 Astronomy & Geology a period of a thousand million years.
3》 Geology a major division of geological time, subdivided into eras.
4》 Philosophy (in Neoplatonism, Platonism, and Gnosticism) a power existing outside time, deriving from the supreme deity.
Origin
C17: via eccles. L. from Gk aiōn 'age'.