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 period

Type of: aeon, eon

• arles
• Arlington
• arm
• arm bone
• arm candy
• arm exercise
• arm in arm
• arm pad
• arm's length
• arm-twisting
• armada
• Armadillidiidae
• Armadillidium
• armadillo
• Armageddon
• Armagnac
• armament
• armamentarium
• Armand Jean du Plessis
• Armata Corsa
• armature
• armband
• armchair
• armchair liberal
• armed