| Word | Meaning |
| Compressed air | Air kept at a pressure higher than atmospheric pressure |
| Compressor | A machine that reduces the volume of air and packs it in |
| Atmosphere | The layer of air that covers the Earth all around |
| Atmospheric pressure | The pressure of air on unit area of the Earth's surface |
| One atmospheric pressure | The pressure at sea level, 760 mmHg |
| Milibar | The unit in which the pressure of compressed air is measured |
| Barometer | The instrument used to measure atmospheric pressure |
| Manometer | An instrument that measures the pressure of a liquid or a gas |
| Air brake | A brake worked by compressed air |