• to act as deputy for sy, to act for sy, to do duty for sy, to stand in, to sub for sy, to substitute for sy, to supply for sy, to supply sy's place, to take over from sy
• to put sy in sy's place, to replace sg by sg, to replace sg with sg, to replace sy by sy, to substitute, to substitute sg for sg, to suffect
• displacement, replacement, substitution
• interchangeable, replaceable, substitutable