acid - alde
- active Q-switching
- active repeater
- active satellite repeater
- active sonar
- active substrate
- active uptake
- active value
- actively locked laser
- actively mode-locked laser
- actively stabilized laser
- actively-stabilized laser
- activin
- activity
- activity equilibrium constant
- activity of catalyst
- activity rhythm
- activity unit
- activity wheel
- actomyosin
- actophilous
