WordWeb Online

1. An event in which one thing is substituted for another
   - permutation, transposition, replacement, switch
    
2. 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"
   - exchange, commutation

Derived forms: substitutions

See also: substitute

Type of: change, fluctuation, variation

Encyclopedia: Substitution