- arithmetic overflow
- arithmetic relation
- arithmetical difference
- ARJ
- arrangement
- array argument
- array computer
- array identifier
- array partitioning
- array size
- arrival sequence
- arrow button
- arrow operator
- article
- artificial reality
- artwork window
- as many
- asbestine tile
- asbestos packing
- ascending key
- ascending node
- ascending note
- ASCII art
- ASCII mode
- askew arch
- asphalt kettle
- asphalt work
- assemble duration
- assembler directive
- assembly phase
- assertion failure
- assets
- assign
- assignment conversion
- Assignment problem
- assisted panel
- associated data
- associative algebra
- associative key
- associative retrieval
- assumption
- artificial horizon
- artificial selected
- ascending condition
- ASCII file
- assemble
- assemble program
- assembling phase
- assembly unit
- assertion
- assigned document
- assignment
- assignment expression
- assignment name
- assignment statement
- assist
- associate elements
- associated document
- associated tensions
- associative law
- associator
- assumption formula
- astronomical time
- asymmetric cryptography
- asymmetric test
- asymptoical distribution
- asymptotic approximation
- asymptotic curvature
- asymptotic point
- asymptotic tangent
- asymptotically stable
- asynchronous communication
- asynchronous device
- asynchronous flow
- asynchronous machine
- asynchronous operation
- asynchronous terminal
- asynchronous transmission
- asyndetic
- AT-compatible
- ATAPI
- atomic
- atomic sentence
- attached
- attached document
- attached file
- attached message
- attached processor
- attached shock
- arabic numerals
- arbitration group
- arc polygon
- arc tangent
- archimede group
- Archimedean group
- archival backup
- archival storage
- archive bit
- archiveability
- arcograph