The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium.

Laws of thermodynamics, four relations underlying thermodynamics, the branch of physics concerning heat, work, temperature, and energy and the transfer of such energy. The first and second laws were formally stated in works by German physicist Rudolf Clausius and Scottish physicist William Thomson.

The First Law of Thermodynamics states that energy can be converted from one form to another with the interaction of heat, work and internal energy, but it cannot be created nor destroyed, under any circumstances.

The laws of thermodynamics describe the relationship between matter and energy and how they relate to temperature and entropy. Many texts list the three laws of thermodynamics, but really there are four laws (although the 4th law is called the zeroeth law).