A replacement or stand-in for something that achieves a similar result or purpose.
A player who is available to replace another if the need arises, and who may or may not actually do so.
One who enlists for military service in the place of a conscript.
A good that a consumer perceives as similar to another good, which decreases the demand for that other good
To use in place of something else, with the same function.
(in the phrase "substitute X for Y") To use X in place of Y.
(in the phrase "substitute X with/by Y") To use Y in place of X; to replace X with Y.
To remove (a player) from the field of play and bring on another in his place.
To serve as a replacement (for someone or something).