Formulation of the laws of conservation and non-conservation

For each substance-like quantity, a theorem about its conservation or non-conservation can be formulated. For the electric charge e.g. it reads: Electric charge can neither be created nor destroyed. Such a statement is short and easy to understand. For some quantities, however, the proposition about conservation or non-conservation is usually formulated in an unnecessarily complicated way. Sometimes the formulation is not generally valid; in other cases only a consequence of the conservation or non-conservation is pronounced. A clear and unified formulation could improve the comprehensibility and simplify teaching.