What does "commutation" mean?

Additional senses

1. 2.(Law) The change of a penalty or punishment by the pardoning power of the State; as, the commutation of a sentence of death to banishment or imprisonment. Suits are allowable in the spiritual courts for money agreed to be given as a commutation for penance. Blackstone.
2. 3.A substitution, as of a less thing for a greater, esp. a substitution of one form of payment for another, or one payment for many, or a specific sum of money for conditional payments or allowances; as, commutation of tithes; commutation of fares; commutation of copyright; commutation of rations. Angle of commutation (Astron.), the difference of the geocentric longitudes of the sun and a planet. -- Commutation of tithes, the substitution of a regular payment, chargeable to the land, for the annual tithes in kind. -- Commutation ticket, a ticket, as for transportation, which is the evidence of a contract for service at a reduced rate. See 2d Commute, 2.