Archaean

• Archean
• Archæan (archaic)

From Ancient Greek ἀρχαῖα (arkhaîa, “ancient”), neuter plural of ἀρχαῖος (arkhaîos, “ancient”).

• (Received Pronunciation) IPA^(key): /ɑːˈkiːən/

• Audio (Southern England):

  (file)

• (General American) IPA^(key): /ɑɹˈkiːən/
• Rhymes: -iən

Archaean (not comparable)

1. (mythology) Of or relating to Arche, the Muse of beginnings in Greek mythology.
2. (geology) Of, or relating to the geologic eon from about 4,031 to 2,500 million years ago; comprises the Eoarchean, Paleoarchean, Mesoarchean and Neoarchean eras; marked by an atmosphere with little oxygen, the formation of the first continents and oceans and the emergence of simple life.
   • 2006 March 25, NewScientist, page 12/1:

     The oldest vestiges of continental crust, which date from the Archaean aeon about 4 billion years ago, are in Acasta in north-west Canada.

3. (astronomy, "Archean" only) Of or relating to the irregular Jovian moon named for Arche.

Archaean

1. (geology) The eon from 2,500 Ma to 4,000 Ma.

• (eon 2,500–4,000 Ma): Precambrian

• (eon 2,500–4,000 Ma): Eoarchaean, Paleoarchaean, Mesoarchaean, Neoarchaean

• (eon 2,500–4,000 Ma): Hadean, Proterozoic - eons in Precambrian

• Appendix:Geologic timescale

• Archaean on Wikipedia.Wikipedia