1. (

• substitution ,
• permutation ,
• transposition ,
• replacement ,
• switch

) an event in which one thing is substituted for another; "the replacement of lost blood by a transfusion of donor blood" ;

2. (

• substitution ,
• exchange ,
• commutation ,

) 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" ;