| Abbreviation | Definition |
|---|---|
| ATC | Automation Tool Company |
| ATK | Available Ton Kilometers |
| AU | Absorbance Units |
| AU | Allocation Unit |
| AU | Arbitrary Units |
| AU | Astronomical Units |
| AU | Atomic Units |
| AUI | Arbitrary Unit of Intensity |
| AUM | Animal Unit Month |
| AVO | Amperes Volts And Ohms |
| AW | Air Watts |
| AWG | American Wire Gauge |
| AWK | Actual Weight in Kilograms |
| B | Bel |
| B | Billion |
| B | Bit |
| B | Bytes |
| bag | bag |
| BAM | Binary Angular Moment |
| BBBLS | Billion Barrels (of oil) |