Define second law of thermodynamic?

The phrase 'second law of thermodynamics' means a law stating that mechanical work can be derived from a body only when that body interacts with another at a lower temperature; any spontaneous...

The second law of thermodynamics states that in a closed system, the entropy of the system does not decrease.

A drop of ink in a glass of water. Drop it in. Count to three while the second law works its magic. Now take it out again.

Heat cannot of itself pass from a colder body to a hotter body.

The entropy of an isolated system will increase over time. Differences in temperature tend to balance, heat flows from high temp. to cold.