Grandparent is right. Entropy is best thought of as a two-parameter function. Not entropy(system), but rather entropy(system, your knowledge of system). The

Grandparent is right. Entropy is best thought of as a two-parameter function. Not entropy(system), but rather entropy(system, your knowledge of system). The system is in a microstate, but you don't know which one. If you did, it would have zero entropy. Since you only have a few general measurements like "one litre of gas at room temperature and one atmosphere of pressure", the entropy is much higher, because many microstates meet that description. If you think of entropy as an objective property of the system regardless of a given observer's state of knowledge, you'll likely get confused.