There are two special significance :
(1) Specific heat of a gas at constant volume (Cv) : It is defined as the quantity of heat required to raise the temperature of unit mass of gas through 1 K when its volume is kept constant.
(2) Specific heat of a gas at constant pressure (Cp) : It is defined as the quantity of heat required to raise the temperature of unit mass of gas through 1 K when its pressure is kept constant.