commutation of sentence
com·mu·ta·tion / ˌkämyəˈtāshən/ • n. 1. action or the process of commuting a judicial sentence. ∎ the conversion of a legal obligation or entitlement into another form, e.g., the replacement of an annuity or series of payments by a single payment. 2. the process of commutating an electric current. 3. Math. the property of having a commutative relation.
J. A. Cannon
Modification, exchange, or substitution.
Commutation is the replacement of a greater amount by something lesser. To commute periodic payments means to substitute a single payment for a number of payments, or to come to a "lump sum" settlement.
In criminal law, commutation is the substitution of a lesser punishment for a greater one. Contrasted with clemency, which is an act of grace eliminating a sentence or punishment, commutation is the modification or reduction of a punishment.
The change from consecutive prison sentences to concurrent sentences is a commutation of punishment.