Substitution
WordNet
noun
(1) 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"
(2) An event in which one thing is substituted for another
"The replacement of lost blood by a transfusion of donor blood"
WiktionaryText
Noun
- the act of substituting or the state of being substituted
- a substitute or replacement
- (especially in organic chemistry) the replacement of an atom, or group of atoms, in a compound, with another