n. A passing from one state to another; alteration; change.n. The act of giving one thing for another; exchange; barter.n. The act of substituting one thing for another; substitution.n. Specifically— In law, the change of a penalty or punishment from a greater to a less, as banishment instead of death.n. The substitution of one sort of payment for another, or of a money payment in lieu of the performance of compulsory duty or labor, or of a single payment in lieu of a number of successive payments, usually at a reduced rate. See commutation-ticket.n. Milit., the money value of allowances, such as quarters, fuel, forage, etc., taken in place of them.