n.

1. 永世；萬古
2. 【地】十億年期

n.

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.