What is a thermodynamic equation of state?

(N/A) thermodynamic equation of state is a mathematical relationship between the state variables that describe the equilibrium state of a thermodynamic system.
For a simple fluid system,the state variables are typically pressure $(P)$,volume $(V)$,and temperature $(T)$.
The equation of state is expressed as $f(P, V, T) = 0$.
For an ideal gas,the equation of state is given by the ideal gas law: $PV = nRT$,where $n$ is the number of moles and $R$ is the universal gas constant.