I agree with you > Substitute X for Y I would read this as saying "use X instead of Y". In contrast, I would use this wording for the opposite intention: > S

I agree with you > Substitute X for Y I would read this as saying "use X instead of Y". In contrast, I would use this wording for the opposite intention: > Substitute Y with X This discussion also adds support to the side that "substitute X for Y" is the correct terminology: https://english.stackexchange.com/questions/23360/substitute-x-for-y https://english.stackexchange.com/questions/23360/substitute... > This is probably the source of the confusion you noticed: > “Substitute…for…”—first replaces second. > “Substitute…with…”—second replaces first. > 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. > 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. I would agree that there is debate, and that your suggestion is the standard (edited as I misread your and the original commenter's sides of the debate)