- alchemist
- alchemy
- alcoholimeter
- airtight
- alarm system
- albedo
- alcoholometer
- Alford loop
- Alfven wave
- alkaline earth
- all-pass
- allomerism
- allomerous
- agonic
- air circuit
- air circulation
- air cleaner
- air cleaning
- air compartment
- air compressor
- air condenser
- air control
- air coolant
- air cooler
- air cooling
- air deflector
- air dehydration
- air density
- air ejector
- air entry
- air guide
- air humidification
- air infiltration
- air injection
- air ionizing
- air oasis
- air pumping
- air purifier
- air reconditioning
- air saturation
- air screen
- air speed
- air stratification
- air termination
- air thermostat
- air-cooled
- airblast thawing
- aircraft cooling
- aircraft station
- Alcomax
- aldehyte
- aliasing
- alidade
- alive
- all-metal
- all-wave
- Allan cell
- allochromatic
- allomeric
- allomorphism
- allotropism
- allotropy
- allowable temperature
- allowed band
- alloy
- alloyed
- alloying
- Alni
- alnico
- alpha decay
- alpha detector
- alpha radioactivity
- alpha-disintegration
- alpha-dosimetry
- alpha-emission
- alpha-function
- alpha-radiation
- alpha-spectroscopy
- alpha-spectrum
- alphatron
- alteration
- alternance
- alternating climate
- alternating current
- alternating field
- alternating gradient
- alternating voltage
- alternative
- alternative refrigerant
- alternator
- altimeter
- alumel
- aluminium conductor
- aluminium fin
- amalgamation
- ambient atmosphere
- ambient temperature
- ambiguous
- ambipolar diffusion
- ambipolar potential