English word Proterozoic comes from English -zoic, English protero- (First, earliest, early.)
| Dictionary entry | Language | Definition |
|---|---|---|
| -zoic | English (eng) | Relating to some specified form of animal existence. Relating to some specified geologic period. |
| protero- | English (eng) | First, earliest, early. |
| Proterozoic | English (eng) | (geology) Of or relating to the geologic eon from 2,500 Ma to 541.0±1.0 Ma. (geology) The eon from 2,500 Ma to 541.0±1.0 Ma, the beginning of the Phanerozoic, marked by the build up of oxygen in the atmosphere and the emergence of primitive multicellular life. |