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An awful lot of people seem to use the phrase "substitute X for Y" to mean "replace X with Y", while I've always used and understood it as "replace Y with X". This makes sense to me, given that a substitute is the replacement, not the thing which has been replaced.

I thought I might be able to figure things out from a dictionary, but now after seeing two sorts of definitions, I'm even more confused:

  1. to put or use in the place of another
  2. to take the place of; replace

The first one suggests that the object will be the substitute (replacement), the thing put into place, while the second suggests that the object will be the thing which has been replaced.

Is one of these usages more correct in any sense? (I know this is probably a pointless question, since people will continue to speak the way they speak.) Is there perhaps a difference between American and British English?

And most importantly, is there any reliable way to tell what someone means when they ask how to substitute honey for sugar, or is the verb simply guaranteed to cause confusion?

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This is probably the source of the confusion you noticed:

  • “Substitute…for…”—first replaces second.
  • “Substitute…with…”—second replaces first.
  • “Replace…with…”—second replaces first.
  • “Replace…by…”—second replaces first.
  • etc.

“Substitute…for…” is an unusual case when it comes to the order of this sort of phrase, but actually the preposition is all-important. Just think of for as meaning in favour of or in place of.

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    I do understand all of these exactly as you say; it was only the second definition which seemed odd, but you've certainly clarified where that one is used. As for the incorrect usage, I guess it's just that - something I have to try to notice and take into account. I'd been half-hoping I was being overzealous and there weren't quite so many people saying the opposite of what they meant. (This is really annoying over on cooking.stackexchange.)
    – Cascabel
    Commented May 1, 2011 at 1:47
  • I think there's a good reason why people don't take much notice of the particular operator specified (for or with). As soon as you hear the word substitute you pretty much know one of the two important words following will already be 'on the table', so to speak (it's in the sentence being considered for revision, for example). Once you identify that 'existing' word, you know the other is a proposed replacement. The third word is effectively just 'noise' in this context, so neither the speaker nor the hearer really care about it.
    – FumbleFingers
    Commented May 2, 2011 at 0:30
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    @FumbleFingers: cooking.stackexchange.com/questions/14440/…
    – Cascabel
    Commented May 2, 2011 at 3:13
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    @Fumble: But the problem is that the OP there is using "for" with the entities swapped, i.e. as if it were "with". And my point was to provide a counterexample to your statement that you generally know which item is the replacement - you don't always!
    – Cascabel
    Commented May 2, 2011 at 14:16
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    "Insert X for Y" is another case where the first term replaces the second. The following is a quote from The Anglo-American Establishment by Carroll Quigley: "In considering questions suggested take Constitution of the Jesuits if obtainable and insert 'English Empire' for 'Roman Catholic Religion.'"
    – nisetama
    Commented Jan 29, 2019 at 2:26
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I agree with Jon and Henry. However, it should be noted that the use of to substitute X with Y is usually not recommended by style books: it is a blend of the old expressions to substitute X for Y and to replace X with Y. It may have emerged out of confusion between the two. You substitute the new thing for the old thing, and you replace the old thing with or by the new thing. There is also simply to substitute X, without a Y:

Petrochemical oil is a very useful type of fuel with a high energy yield; if we substitute vegetable oil, we may have less pollution, but we'll need larger fuel tanks.

This use of the verb to substitute X as above is quite common; you always substitute a new thing, vegetable oil. What you substitute it for is then implicit; in this case, it would be the petrochemical oil from the first clause. It fits with to substitute X for Y (you substitute the new thing), but it clashes with to substitute X with Y; that is another reason not to use the latter.

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The preposition controls the meaning. "Substitute X for Y" means what you think it does: the X will replace Y.

"Substitute X with Y", however, reverses the meaning: Y will replace X.

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  • -1. What controls the respective meanings of the direct object X and the prepositional object Y is not the preposition but the verb, as others have stated. The second paragraph here is wrong and misleading, and doesn't deserve to be here, misleading future readers.
    – Rosie F
    Commented May 4, 2019 at 6:20
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The traditional construction is like this:

The mechanic had to substitute a generic steering wheel for the original Bentley wheel.

The substitute is the thing you substitute; the original is what you substitute it for. It is perhaps easier to remember if you know the origin of the construction. The word substituo means "to place under, to substitute" in classical Latin. From statuo, "to place, to cause to stand", and sub-, "under". The prefix sub- is used in a way similar to supplant, suppose, the latter meaning "to take a theory in place of a fact" (we suppose something because we don't have the facts).

It is also possible to mention only the substitute:

The recipe said she needed "bacon". She hated bacon. She decided to substitute parma ham.

Because some people have forgotten how to use the construction, probably caused in part by contamination with replace, you will sometimes see it used in various other ways; however, because confusion is quick to ensue, style guides recommend that you use it like this.

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  • That does not ring true in my easy - I strongly miss it for or it with parma ham in the second part... Am I correct or just non-native ;)
    – mplungjan
    Commented Jul 15, 2012 at 8:48
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    @mplungjan: With is strictly speaking also a contamination with replace. As to substitute without for, you can see a few examples from books here: google.com/…
    – Cerberus - Reinstate Monica
    Commented Jul 15, 2012 at 9:06
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    Yes. The two verbs have complementary syntax. One replaces Old with New, but substitutes New for Old. Rather like one buys Commodity for $$ vs pays $$ for Commodity. The prepositions vary all over the lot, of course; but then they always do.
    – John Lawler
    Commented Jul 15, 2012 at 16:45
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    @mplungjan If you wanted to be more explicit like that, and use the verb "substitute", the way to say it is "She decided to substitute parma ham for it".
    – Rosie F
    Commented May 4, 2019 at 6:17
  • "...for it" in your example is implied, but not necessary, as it is clear from the preceding sentence what the parma ham would replace.
    – Dustin G
    Commented Mar 26, 2023 at 10:32
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That’s fine if you put it in two sentences like that, it becomes clarified by context. But too many people describing recipes will get it wrong where the context really does matter. For example:

I used my grandmother’s recipe, but I substituted apples for pears.

That sentence above is totally unclear, particularly if you don’t have access to Grandmother’s recipe. This should correctly mean that Grandma specified pears, but I used apples instead. But 80% of people would interpret this the opposite way. The result is confusion.

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    In a comment to another answer, @FumbleFingers wrote "Mostly you can tell which elements to substitute simply by looking to see which one you've already got!" This is a good example to show that that just isn't true -- because the sentence isn't about what a reader unknown to the writer has already got.
    – Rosie F
    Commented May 4, 2019 at 6:14
  • The sentence above is perfectly clear. If someone interprets it the opposite way, it's because of a poor facility for English.
    – Dustin G
    Commented Mar 26, 2023 at 10:49

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