Conservation law

Conservation law is a physical law that says that some physical quantity is conserved, which means never changes. Examples of conserved quantities in physics are energy and momentum along 3 axies. So we have at least 4 independent conservation laws of momentum around axis 1, momentum around axis 2, momentum around axis 3, and energy, that is considered axis 4 by some autors or axis 0 by others. Usually mathematicians use diferent convention for numbering axes than physicists, who number axes starting from 0 for energy, and so on for other axes (e.g. t, x, y, z where t denotes time, and the rest relate to space).