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Can someone please specify the correct usage of the word "substitute" (verb)?

For example, "You can substitute X for Y."?

Dictionary definitions that I have seen do not make it obvious, and I think I've heard its use in casual conversation both ways. I'm pretty sure that correct usage in the above example has the following sense: "You can use X instead of Y.", but can anyone provide a authoritative source that is explicit about this?


You are correct, "to substitute X for Y" means that X is the new, Y is the old. A synonym would be "to replace Y with X". The phrase "substitute X for Y" cannot have the opposite meaning, and I think the principle factor is the word "for". If you understand computer logic, you could rephrase it this way, where "for" = "if exists": if exists Y, substitute X. The preposition "for" does not admit the inverse sense, unlike Spanish and other Romance languages. —Stephen 06:49, 7 June 2006 (UTC)
Unfortunately, both meanings are used: "substitute Y with X". When "with X" is omitted the result is ambiguous, and the possible effects can be horrendous to contemplate. I've added a cautionary note. --Thnidu (talk) 23:50, 10 December 2014 (UTC)


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"I had to substitute old parts with the new ones" is horrible English, and you do your readers a disservice by presenting it as correct. The statement in the Usage notes that the reader or hearer cannot tell what is meant by "Substitute butter" or "Substitute olive oil" is also incorrect. Perhaps this is true for the reader who does not understand the meaning of the word "substitute", but for anyone who does understand, the meaning is clear. 04:50, 27 December 2014 (UTC)

I agree with you about the modern trend to use substitute with instead of replace with, (and the even worse use of "by") but the OED says: "This use was often criticized in the early 20th cent., and replace preferred; N.E.D. (1914) comments: ‘Now regarded as incorrect.’ However this use of substitute (particularly in the passive voice) remains common." so, as a descriptive dictionary, we have to accept that people "misuse" the construction and that this misuse has become "normal". I'd be surprised if many "good" writers use the "horrible" construction. Because of this "misuse", many people no longer understand the correct use of the example in the usage note. Perhaps we could just note that the construction with "with" was formerly proscribed? Dbfirs 11:05, 27 December 2014 (UTC)
Linguists as scientists describe language, they don't dictate it. You wouldn't get physicists commenting on whether particles spin the right or the wrong way. It would be ridiculous. Renard Migrant (talk) 17:56, 22 April 2015 (UTC)
Historians don't hide history just because they don't like it. If your physicist discovered that a particle used to spin the other way, then that would certainly be worth recording. Dbfirs 19:49, 22 April 2015 (UTC)