The Laws of Thermodynamics
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In thermodynamics, there are four laws of very general validity, and as such they do not depend on the details of the interactions or the systems being studied. Hence, they can be applied to systems about which one knows nothing other than the balance of energy and matter transfer. Examples of this include Einstein's prediction of spontaneous emission around the turn of the 20th century and current research into the thermodynamics of black holes.

Zeroth law of thermodynamics, about the transitivity of thermodynamic equilibrium.
If two thermodynamic systems A and B are in thermal equilibrium, and B and C are also in thermal equilibrium, then A and C are in thermal equilibrium.

First law of thermodynamics, about the conservation of energy.
The increase in the energy of a closed system is equal to the amount of energy added to the system by heating, minus the amount lost in the form of work done by the system on its surroundings.

Second law of thermodynamics, about entropy.
The total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.

Third law of thermodynamics, about absolute zero temperature.
As a system approaches absolute zero of temperature all processes cease and the entropy of the system approaches a minimum value or zero for the case of a perfect crystalline substance.