or ideal gas
Gas whose physical behaviour conforms to the general gas law , which states that for a given quantity of gas, the product of the volume V and pressure P is proportional to the absolute temperature T , or P V = k T , where k is a constant.
A perfect gas is assumed to consist of a large number of molecule s in random motion, which obey Newton's laws of motion . Their volume is assumed to be negligibly small, and no forces are presumed to act on the molecules except during momentary collisions. Though no gas has these properties, real gases at sufficiently high temperatures and low pressures can be described this way.