100 - adju
- 100 metre mark
- 100 metre stake
- a-battery
- a-digit
- a-digit selector
- a-eliminator
- a-frame
- A-operator
- a-selector
- A-unit
- a.c. to d.с. system
- a.c.-system
- AB brake equipment
- abandon
- abandoned call
- abatement of smoke
- abc-power unit
- ability rating
- above surface housing
- above the standard
- above-earth potential
- above-ground storage tank
- abrade
- abrading
- abrading action
- abrasion
- abrasion of rails
- abrasion resistance
- abrasion test of lubricant
- abrasive
- abrasive cleaning cloth
- abrasive fly ash
- abrasive resistance
- abrasive wear
- abrasives
- abreast
- abrupt taper
- absence of smoke
- absolute block
- absolute block section
