substitution

noun

1. an event in which one thing is substituted for another

   noun.event

   Synonyms permutation replacement switch transposition

   Source: WordNet 3.0

2. the act of putting one thing or person in the place of another:

   noun.act

   Examples

   He sent Smith in for Jones but the substitution came too late to help.

   Synonyms commutation exchange

   Source: WordNet 3.0

3. The act of substituting or putting one person or thing in the place of another; as, the <i>substitution</i> of an agent, attorney, or representative to act for one in his absense; the <i>substitution</i> of bank notes for gold and silver as a circulating medium.

   noun

   Source: webster1913