1. The period from about 540 million years ago until the present
   - Phanerozoic, Phanerozoic eon

Type of: aeon, eon

• broken home
• broken in
• broken wind
• aztreonam
• azure
• azure aster
• azurite
• azygos
• azygos vein
• azygous
• azygous vein
• azymia
• b
• B battery
• B cell
• B complex
• B lymphocyte
• B movie
• B vitamin
• B-52
• B-complex vitamin
• B-flat clarinet
• B-girl
• B-horizon
• b-meson