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"

substitute a person or thing for (another that is broken or inefficient or lost or no longer working or yielding what is expected)

take the place or move into the position of

(law) the replacement of one obligation by another by mutual agreement of both parties; usually the replacement of one of the original parties to a contract with the consent of the remaining party

replacing a pitcher in baseball

act of replacing one person or thing by another especially one held to be superior

act of taking the place of another especially using underhanded tactics