| The American Heritage® Dictionary of the English Language: Fourth Edition. 2000. |
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| Archean |
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| SYLLABICATION: | Ar·che·an |
| PRONUNCIATION: |  är-k   n |
| VARIANT FORMS: | also Ar·chae·an |
| ADJECTIVE: | 1. Of or belonging to the earlier of the two divisions of Precambrian time, from approximately 3.8 to 2.5 billion years ago, marked by an atmosphere with little free oxygen, the formation of the first rocks and oceans, and the development of unicellular life. See table at geologic time. 2. Of or relating to the oldest known rocks, those of the Precambrian Eon, that are predominantly igneous in composition. | | NOUN: | The Archean Eon. Also called Archeozoic. | | ETYMOLOGY: | From Greek arkhaios, ancient. See archaic.
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| The American Heritage® Dictionary of the English Language, Fourth Edition. Copyright © 2000 by Houghton Mifflin Company. Published by the Houghton Mifflin Company. All rights reserved. |
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