- ancestral relation
- anchor
- anchor cell
- anchor screw
- antenna bandwidth
- antenna gain
- anti logarithm
- anti-automorphic
- anti-chain
- anti-collinear
- anti-correlation
- anti-dual
- anti-fading
- anti-isomorphism
- anti-noise
- anti-oscillating
- anti-representation
- anti-symmetric
- anti-tangent
- anticipate
- anticipatory
- anticipatory buffering
- anticipatory control
- anticipatory paging
- anticipatory staging
- anticoincidence
- anticoincidence element
- anticoincidence function
- anticollineation
- anticorrelation
- anticyclone
- antifouling paint
- ancillary information
- AND function
- AND gate
- AND operation
- AND operator
- aneroid
- angle beam
- angle iron
- angular measure
- angular point
- animated
- animated template
- animation software
- annotation style
- announcement
- annual income
- annular
- annunciator
- anode neutralization
- anode voltage
- anonymous
- answer
- answer mode
- answering
- answering key
- antenna loading
- antigens
- antigenus
- antihomomorphism
- antihunting circuit
- antiinterference
- antiparallel lines
- antipodal
- antipodal point
- antiprojectivity
- antiradical
- antistatic device
- antistatic mat
- antisymmetric matrix
- antisymmetrization
- antithesis
- antithetic procedure
- antithetical
- antithetical procedure
- antivirus software
- any
- any character
- any type
- any-mode
- apache
- aperiodic circuit
- aperiodic group
- aperiodic oscillation
- aperiodic state
- aperture card
- aperture correction
- aphelion
- apogee
- apostrophe
- apothem
- apparent distance
- apparent mass
- apparent singularity
- append
- appendage
- appendage routine
- appendage task
- apple