Microstate and Macrostate

Definition: Microstate and Macrostate

Suppose we have two parameterisations $P_1$ and $P_2$ of a physical system with $n_1$ and $n_2$ parameters, respectively.

If $n_1<n_2$ and the values of all parameters in $P_2$ can be determined if we know the values of all parameters in $P_1$, then any physical state from $P_1$ is called a microstate and any physical state from $P_2$ is called a macrostate.