substitution (n.)

late 14c., substitucion, "appointment of a subordinate or successor," from Old French substitucion, substitution or directly from Late Latin substitutionem (nominative substitutio) "a putting in place of (another)," noun of action from past-participle stem of Latin substituere "put in place of another, place under or next to, present, submit," from sub "under" (see sub-) + statuere "set up" (from PIE root *sta- "to stand, make or be firm," with derivatives meaning "place or thing that is standing").