com·mu·ta·tion /ˌkɑmjəˈteʃən/
 交換,變換,代替
 Com·mu·ta·tion n.
 1. A passing from one state to another; change; alteration; mutation. [R.]
    So great is the commutation that the soul then hated only that which now only it loves.   --South.
 2. The act of giving one thing for another; barter; exchange. [Obs.]
    The use of money is . . . that of saving the commutation of more bulky commodities.   --Arbuthnot.
 3. 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.
 4. 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.
 5. regular travel from a place of residence to a place where one's daily work is performed; commuting.  Most often, such travel is performed between a suburb and a nearby city.
 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.
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 commutation
      n 1: the travel of a commuter [syn: commuting]
      2: a warrant substituting a lesser punishment for a greater one
      3: (law) the reduction in severity of a punishment imposed by
         law [syn: re-sentencing]
      4: the act of putting one thing or person in the place of
         another: "he sent Smith in for Jones but the substitution
         came too late to help" [syn: substitution, exchange]