I just have this confusion which is completely eating me up. They say entropy of a system is a state property. Then they say that for a completely isolated system, entropy either increases or remains zero depending on the process being irreversible or reversible. So, let's say for an isolated system I go from A to B thru a reversible path then entropy is zero. And if I go thru an irreversible path, it's something else. But if entropy is a state property, how can it be different for the two paths between same points? This completely makes no sense to me.