[sub.sti.tute] n [ME, fr. L substitutus, pp. of substituere to put in place of, fr. sub- + statuere to set up, place--more at statute] (15c): a person or thing that takes the place or function of another -- substitute adj
[2]substitute vb -tut.ed ; -tut.ing vt (1588) 1 a: to put or use in the place of another b: to introduce (an atom or group) as a substituent; also: to alter (as a compound) by introduction of a substituent "a substituted benzene ring"
2: to take the place of: replace ~ vi: to serve as a substitute