Conservation Law
A conservation law states that a particular quantity remains unchanged as a system evolves. It may be transferred or transformed within the system, but it is neither created nor destroyed. An invariant is a quantity, relationship, or property that remains unchanged under the allowed transformations of a system. A conservation law describes what is conserved. An invariant is the mathematical expression of that conservation. A conservation law is a principle; an invariant is the quantity or equation that stays unchanged because of that principle. Here are three examples of systems that adhere to the notion of conservation law: Physics : conservation of energy; energy is not created or destroyed; the energy just moves; the invariant is total energy. Chemistry : conservation of mass (atoms); the inventory of atoms does not change; the count of each atomic species is the invariant. Accounting : conservation of resources and obligations; the resources must always equal the claims on tho...