Reduced temperature and pressure are defined as: $\begin{gather}T_R = \frac{T}{T_c} \qquad P_R = \frac{P}{P_c}\end{gather}$ where $T_c$ and $P_c$ are *[[Critical point|critical]]* temperature and pressure and $T$ and $P$ are the actual temperature and pressure. $T_R$ and $P_R$ are used in several methods of calculating [[Equations of State - beyond the Ideal Gas Law]] - [!] Not to be confused with [[Residual Properties]]