1. The eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago
   - Precambrian, Precambrian eon, Precambrian aeon

Type of: aeon, eon

• unambiguous
• unambiguously
• unambitious
• unambitiously
• unamended
• unamusing
• unanalysable
• unanalysed
• unanalyzable
• unanalyzed
• unanchored
• unangry
• unanimated
• unanimity
• unanimous
• unanimously
• unannealed
• unannounced
• unanswerable
• unanswered
• unanticipated
• unapologetic
• unappareled
• unapparelled
• unapparent