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 definition: Eon, a variation of aeon, is defined as a unit of geological time equal to a billion years, or a very long period of time. (noun) An example of an eon is the unit of measure used when talking about how long ago the solar system wa...