Answer:
Entropy:
Entropy is the measure of randomness of system.In other words the entropy is the measurement of tendency of system towards the disorder.
The concept of entropy arise from second law of thermodynamics.It is given as follows
Entropy is a extensive property of system .
Entropy of universe = Entropy of system + Entropy of surrounding.
The entropy of the system can be zero,positive and negative.But entropy of the surrounding can not be negative,but it can be zero or positive.
Actually the concept of entropy is difficult to understand because we can not visualize because it is not like beam and like rods.Only we have to realize that there is entropy.