The verb substitute has very different understandings depending on the prepositional company it keeps. For example, ask a barista, Can I substitute regular milk for lactose-free milk? and you’re usually asking for regular milk, not lactose-free. However, if you change the for to with and ask, Can I substitute regular milk with lactose-free milk, then you’re usually specifying that you want lactose-free milk. There’s an important difference between those two, and not everyone understands what is replacing what, so it’s best to choose a different word besides substitute. In an essay included in the book One Language, Two Grammars?: Differences between British and American English (Bookshop|Amazon), linguist David Denison reveals the twisted history of the verb substitute and the strikingly similar path taken by its French cognate. This is part of a complete episode.
