Equilibrium point, operating points

We use the term "equilibrium point" as a mathematically precise description of a point in the state space at which the system is at equilibrium. Avoid the use of the term "equilibrium" to describe such a state, although it is OK to use equilibrium as an adjective for other words ("equilibrium value") or to say a system is "at equilibrium". The term "equilibria" should be avoided; use "equilibrium points" instead.

We the the term "operating point" as a less precise description of a state in which the system might be operating. An operating point is usually an equilibrium point, but there may be other factors involved in the operating point (system condition, operating modes, etc). We generally use the term operating mode when we are not using specific equations, but describing more general situations.