see aeon. another spelling of aeon (aion ). Long span of geologic time. In formal usage, eons are the longest portions of geologic time (eras are the second-longest). Three eons are recognized: the Phanerozoic Eon (dating from the present back to the beginning of the Cambrian Period), the Proterozoic Eon, and the Archean Eon. Less formally, eon often refers to a span of one billion years. Archean Eon Archeozoic Eon Archaean Eon Phanerozoic Eon Proterozoic Eon
(Gnosticism) a divine power or nature emanating from the Supreme Being and playing various roles in the operation of the universe an immeasurably long period of time the longest division of geological time