[sub.sti.tu.tion] n [ME substitucion, fr. MF substitution, fr. LL substitution-, substitutio, fr. substituere] (14c) 1 a: the act, process, or result of substituting one thing for another b: replacement of one mathematical entity by another of equal value
2: one that is substituted for another -- sub.sti.tu.tion.al adj -- sub.sti.tu.tion.al.ly adv -- sub.sti.tu.tion.ary adj