1. A time signature indicating four beats to the bar
   - common time, four-four time, common measure

Type of: musical time

• genus Apteryx
• genus Apus
• genus Aquila
• genus Aquilegia
• genus Ara
• genus Arabidopsis
• genus Arabis
• genus Arachis
• genus Aralia
• genus Aramus
• genus Aranea
• genus Araneus
• genus Araucaria
• genus Araujia
• genus Arbutus
• genus Arca
• genus Arcella
• genus Arceuthobium
• genus Archaeopteryx
• genus Archaeornis
• genus Archeopteryx
• genus Archidiskidon
• genus Archilochus
• genus Architeuthis
• genus Archosargus