- axial compression
- axial fan
- axial flow
- axial force
- axial mode
- axial tension
- axial torque
- axial velocity
- axle bearing
- axle bush
- axle-pin
- axon
- axonometric projection
- azeotropic fluid
- azimuth beam
- azimuth distortion
- azimuth resolution
- azimuth thrust
- azimuthal angle
- automatic tipper
- automatic translation
- automatic transmitter
- automatic typewriter
- automatic welding
- automatic working
- automatize
- autopiler
- autoplotter
- autoradiograph
- autoranging
- autotest
- autotransformer
- autotune transmitter
- autumn
- auxiliary apparatus
- auxiliary department
- auxiliary entrance
- auxiliary gearbox
- auxiliary machine
- auxiliary memory
- auxiliary operation
- auxiliary shop
- auxiliary spring
- availability
- available energy
- available precipitation
- avalanche current
- avalanche effect
- avalanche injection
- avalanche multiplication
- avalanche photodiode
- avalanche triode
- average deviation
- average frequency
- average life
- average traffic
- average value
- average velocity
- average year
- averaging rectifier
- aviation
- aviation fuel
- aviation service
- awry
- axial
- axial deposition
- axial elongation
- axial filament
- axial line
- axial ventilator
- axis
- axle bushing
- axle lathe
- axled
- azeotropic mixture
- azimuth angle
- azimuth compass
- azimuth dial
- azimuth line
- azimuthal component
- azotes
- azurite
- azusa
- B battery
- B-size
- babbit lining
- babble
- babbling network
- bable
- bable clamp
- baby
- bachelor flat
- back
- back action
- back balance
- back board
- back boxing
- back center
- back coat
- back conduction