1 Simple molecules [molecule: A molecule is a collection of two or more atoms held together by chemical bonds. 2  It is the smallest part of a substance that displays the properties of the substance.
Eon has a number of meanings. In Astronomy, an eon refers to 1 billion (109) years. But it also refers to a very long, unspecified period of time, or specific geologic stages of the Earth.
eon; aeon. Hypernyms (eon is a kind of...): geologic time; geological time (the time of the physical formation and development of the earth (especially prior to human history)) Meronyms (parts of eon): era; geological era (a major division of geological time; an era is usually divided into two or more periods) Instance hyponyms: