One frequently hears the verb "substitute" used in an incorrect backward fashion. For example, one may hear "I would like to substitute French fries with mashed potatoes" instead of the correct "I would like to substitute mashed potatoes for the French fries." "Substitute" always refers to the item or person being replaced. It's very hard to get people to see this distinction. If one were to use the word "exchange", it could be used either way, but "substitute" is directional, so to speak.

  • But you’ve also changed the with to for, that changes the direction. – Jim Dec 9 '17 at 20:31
  • I think that this is an interesting question. In a similar vein, I have noticed frequent use of both "sub[stitute] out" and "sub[stitute] in" as verb phrases—meaning essentially the same thing as "swap out" and "swap in"—which may have some bearing on the popular sense that substitute can function bidirectionally as a verb. – Sven Yargs Dec 9 '17 at 21:47
  • It isn't incorrect. It works the same as exchange, swap, or trade. You can exchange A for B, or you can exchange B with A. The choice usually revolves around focus. Do you particularly want something, or do you particularly not want something? Can I substitute the OEM oil filter with a generic that costs less? You could ask (but nobody does) "can I substitute a less costly generic filter for the OEM one?" High valence verbs with prepositional phrase arguments are pretty loose order-wise. Trading my A for your B is typical, but not mandatory. We could trade your B for my A instead. – Phil Sweet Dec 10 '17 at 2:30
  • It is not the same as exchange in my opinion and that of most references. The Oxford English dictionary uses a faulty analogy in trying to draw a parallel between the nonstandard usage and sports usage for substituting a player. They do however admit that the looser usage leads to imprecision. – Dustin G Dec 10 '17 at 5:08
  • It is not I who changed the preposition from for to with; that is the construction of those who wish to use it in the backward sense. – Dustin G Dec 10 '17 at 5:11

This "incorrect" usage has been around for a long time.

The OED says:

Use in this sense has been sometimes criticized (as with sense 3a), but is now generally regarded as part of normal standard English.

And their first citation for this sense is:

1839 tr. C. P. de Kock Barber of Paris I. iv. 92 I carried off a rabbit from the spit, and substituted it with the cat of my old aunt.

  • 1
    Also, from a debate on relief to land purchases (February 2, 1821), in Debates and Proceedings in the Congress of the United States, volume 37: "This amendment Mr. LOWRIE moved to substitute with the deduction of twenty-five per cent." (The bill had previously set the allowable discount at 37.5 percent.) – Sven Yargs Dec 9 '17 at 21:37
  • That just shows that the incorrect usage has been around for a while. – Dustin G Dec 10 '17 at 5:03
  • But this explains why people use it (if that was your question). They grew up hearing other people use it. That's the way language changes. A few people made a mistake 200 years ago, other people repeated it without realizing it was wrong, and today it's become an accepted usage of the word substitute. – Peter Shor Dec 11 '17 at 12:38
  • In the words highlighted in the link I included in my comment above, purchases should be purchasers. – Sven Yargs Dec 13 '17 at 19:22

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