COMMUTATION [Lat. commutare, to change], a process of exchanging one thing for another, particularly of one method of payment for another, such as payment in money for payment in kind or by service, or of payment of a lump sum for periodical payments. (See ANNUITY; COPYHOLD and TITHES.) In law, the substitution of a lesser sentence on a criminal for a greater. In electrical engineering, the reversal of the course of an electric current, by means of a contrivance known as a "commutator" (see DYNAMO). In the United States a "commutation ticket" on a railway is the equivalent of an English season-ticket, and the ticket-holder is known as a "commuter."