noun
Usage: usually capitalized W
Etymology: after Johannes D. van der Waals died 1923 Dutch physicist
: an equation that defines the physical state of a homogeneous gas, is a modification of the ideal-gas equation, and more nearly describes the properties of actual gases: (p+ ( a/v ² )) (v-b)=RT where p is the pressure, v the specific volume, R the gas constant, T the absolute temperature, and a and b are constants depending respectively on the cohesion between the molecules and the volume occupied by the molecules — compare gas law c