- A battery
- A phase
- a positive
- a priori
- A-submarine
- A15 phases
- abbreviated dialing
- abfarad
- ablation
- Able refractometer
- above-critical
- above-thermal
- aboveground storage
- absolute atmosphere
- absolute entropy
- absolute expansion
- absolute scale
- absolute zero
- absorbed horsepower
- absorbed substance
- absorbent charging
- absorptiometer
- absorption
- absorption broadening
- absorption chiller
- absorption line
- absorption refrigeration
- absorption solution
- absorption system
- absorption unit
- acceleration transducer
- accelerogram
- acceptance test
- acceptor centre
- access door
- accessibility
- accommodation area
- accumulated cold
- accumulating counter
- aa
- aAcm2
- ab initio
- abcoulomb
- aberration measure
- abhenry
- Able number
- Abney effect
- abnormal reflections
- absolute alarm
- absolute brightness
- absolute electrometer
- absorber
- absorbing apparatus
- absorbing chamber
- absorption cabinet
- absorptivity
- abstructure
- abundance
- abvolt
- ac
- AC bias
- ac bridge
- abrasive
- absolute permeability
- absolute wavemeter
- absorbable
- absorbent charge
- absorbent solution
- absorber charge
- absorptiometry
- absorption case
- absorption counter
- absorption dehumidifier
- absorption inductor
- absorption meter
- absorption plant
- absorption refrigerator
- accelerated
- accelerated test
- accelerating anode
- accelerating torque
- acceleration sensor
- access channel
- access level
- access point
- accidental degeneracy
- acceleration switch
- acceptable level
- acceptor
- acceptor circuit
- access duct
- accessible compressor
- aCcm
- accordion cable
- achromat
- achromatic lens
- acid stability
- acline
- acoumeter
- acoustic absorption