Pressure (symbol: p or sometimes P)'s the force per unit area applied to an object in a direction perpendicular to the surface. Gauge pressure's the pressure relative to the local atmospheric or ambient pressure. Definition Pressure's an effect which occurs when a force's applied on a surface. The symbol of pressure's p (lower case). Formula Mathematically: » p = frac where: » p's the absolute pressure of the gas n's the amount of substance (in [mole]) » T's the temperature (in kelvin) V'… (More on Pressure)