quantitykind:HeatCapacityRatio
The heat capacity ratio, or ratio of specific heats, is the ratio of the heat capacity at constant pressure ($C_P$) to heat capacity at constant volume ($C_V$). For an ideal gas, the heat capacity is constant with temperature ($\theta$). Accordingly we can express the enthalpy as $H = C_P*\theta$ and the internal energy as $U = C_V \cdot \theta$. Thus, it can also be said that the heat capacity ratio is the ratio between enthalpy and internal energy.