The total entropy of a system and its surroundings always increases for a spontaneous process. This is a statement of

second law of thermodynamics

Explanation:

According to the second law of thermodynamics, the total entropy of a system and its surroundings always increases for a spontaneous process.

Entropy is defined as the degree of disorderliness of a system. The entropy of a system never remains constant. It either increases or decreases in a process. The total entropy is the sum of the entropy of the system and its surrounding. The total entropy must increase in a spontaneous process.

Thus, the implication of this law is that even, if the entropy of a system decreases, this must be compensated for by increase in entropy of the surroundings in order for the process to be spontaneous.