(i) Gauge pressure: Gauge pressure is defined as the difference between actual pressure and atmospheric pressure.
Gauge pressure= Pabsolute – Patmospheric
(ii) Atmospheric pressure: Atmospheric pressure is also called as barometric pressure, is the pressure exerted by the weight of air in the atmosphere.
(iii) Differential pressure: Differential pressure is a pressure that is measured relative to the pressure in the atmosphere around it. It shows the difference between two pressures of the same unit.