**Definition : **The pressure at a point in a fluid in hydrostatic equilibrium is defined as the normal force per unit area exerted by the fluid on a surface of infinitesimal area containing the point.

Thus, the pressure, p = lim_{ΔA→0 }\(\frac{F}{ΔA}\) where F is the magnitude of the normal force on a surface of area ∆A. The pressure is defined to be a scalar quantity.

SI unit: the pascal (Pa), 1 Pa = 1 N∙m^{-2} CGS unit: the dyne per square centimetre (dyn/cm^{2})

**Dimensions : **[p] = [F][A^{-1}] = [MLT^{-2} , L^{-2}] = [ML^{-1}T^{-2}]