substitute

Etymology

From Middle English substituten, from Latin substitutus, past participle of substituō.

verb

1. (transitive) To use in place of something else, with the same function.
   I had no shallots so I substituted onion.
2. (transitive, in the phrase "substitute X for Y") To use X in place of Y.
   I had to substitute new parts for the old ones.
3. (transitive, formerly proscribed, in the phrase "substitute X with/by Y") To use Y in place of X; to replace X with Y.
   I had to substitute old parts with the new ones.
4. (transitive, sports) To remove (a player) from the field of play and bring on another in his place.
   He was playing poorly and was substituted after twenty minutes
   Mario Balotelli replaced Tevez but his contribution was so negligible that he suffered the indignity of being substituted himself as time ran out, a development that encapsulated a wretched 90 minutes for City and boss Roberto Mancini. April 11, 2011, Phil McNulty, “Liverpool 3 - 0 Man City”, in BBC Sport
5. (intransitive) To serve as a replacement (for someone or something).
   Accumulation of wealth by this route may substitute for personal saving. 1987, James Tobin, Essays in Economics, Vol. 2, page 75

noun

1. A replacement or stand-in for something that achieves a similar result or purpose.
   Since you left me, if you see me with another girl / Seeming like I'm having fun / Although she may be cute, she's just a substitute / Because you're the permanent one 1965, “The Tracks of My Tears”, in Going to a Go-Go, performed by Smokey Robinson and The Miracles
   Here we go. AK-47. The very best there is. When you absolutely, positively got to kill every motherfucker in the room, accept no substitutes. 1997, Quentin Tarantino, Jackie Brown, spoken by Ordell Robbie (Samuel L. Jackson)
2. (sports) A player who is available to replace another if the need arises, and who may or may not actually do so.
   Dean Whitehead opened the scoring shortly after the break with a low finish and substitute Peter Crouch sealed the win with a tap-in. 3 November 2011, David Ornstein, “Macc Tel-Aviv 1 - 2 Stoke”, in BBC Sport
3. (historical) One who enlists for military service in the place of a conscript.
4. (economics) Abbreviation of substitute good.