Precambrian

• Pre-Cambrian

pre- +‎ Cambrian

Precambrian (not comparable)

1. (informal, geology) Relating to the time and geology dated before the Phanerozoic

Precambrian

1. (geology) The eon (or supereon) and rock formations dated before 541.0±1.0 million years ago, coinciding with the first appearance of the fossils of hard-shelled animals.

• The International Commission on Stratigraphy, which attempts to standardize the vocabulary of the field, is revising the boundaries between time periods based on physical-science methods rather than the kinds of fossils present.
• The boundary between the Precambrian and the Phanerozoic has been changed from time to time and will be subject to change, as will the eons listed as Hyponyms below.

• (geological eon): Cryptozoic (archaic)

• (geological eon): Hadean, Archaean, Proterozoic - eons

• (geological eon): Phanerozoic