"substitutions" in the noun sense
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"
Source: WordNet® (An amazing lexical database of English)
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