- active state
- active storage
- active subfile
- active volume
- active window
- ActiveX
- activity
- activity attributes
- activity light
- activity ratio
- activity trail
- actual
- actual address
- actual argument
- actual element
- actual error
- actual infinity
- actual parameter
- actual size
- actual throat
- actuarial statistics
- actuator
- acute arch
- acyclic complex
- acyclic machine
- ad absurd
- acidification
- acknowledge character
- ACODE file
- acoustic
- acoustic coupling
- acoustic detector
- acoustic fidelity
- acoustic hood
- acoustic memory
- acoustic panel
- acoustic reactance
- acoustic refraction
- acoustic resistance
- acoustic scattering
- acoustical feedback
- acoustical frequency
- acoustical impedance
- acoustical scintillation
- acoustical wave
- acoustoelectric effect
- acquisition
- ACRnet
- action
- action attack
- action code
- action current
- action diagram
- action frame
- action list
- action paper
- Action Setting
- actual instruction
- actual test
- actuating mechanism
- acute angle
- acute triangle
- acuteness
- acyclic
- acyclic function
- acyclic graph
- acyclicity
- ad
- ad-infinite
- Ada compiler
- Ada language
- adaptation layer
- adapter card
- adapter check
- adaptive
- adaptive communication
- adaptive device
- adaptive filter
- adaptive filtering
- adaptive system
- adaptor card
- add circuit
- add gate
- add mode
- add-on
- adder accumulator
- adder-subtracter
- addition
- addition record
- additional character
- additional function
- additive
- additive category
- additive decomposition
- additive functor
- additive group
- additive process
- additivity
- address 1 code
- address bit