eon
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About Our Definitions: All forms of a word (noun, verb, etc.) are now displayed on one page.eon
eon
noun (Concise Encyclopedia)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.
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