Now that you know how entropy is formally defined, let us have a closer look at this definition: entropy counts the number of microstates that can give rise to a certain macrostate. Notice the word can. The state of a system is always in only one microstate. The statement that it “can” be in any other state is counterfactual—it refers to states that do not exist in reality; they exist only mathematically. We consider them just because we do not know exactly what the true state of the system is.
