English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Key to exercises.

Today I saw the quoted sentence when looking at the keys to exercises, and afterwards that sentence got me thinking why the preposition to is used here instead of for.

The way I see it is that the key purpose is to match our answer with the correct one; hence, for would fit here nicely. Am I right?

share|improve this question
Because keys in the standard sense go to locks. – cornbread ninja 麵包忍者 Aug 9 '12 at 20:33
I've heard them used interchangeably, so the answer might well be subtle or paved over by misuse. – rsegal Aug 9 '12 at 20:50
If I'm understanding this question correctly, I would simply use the term "Answer Key" and avoid the preposition altogether. – J.R. Aug 9 '12 at 20:56
I suspect there is a similar principle in effect when stating "the answer to your question is" versus "the answer for your question is", but I don't know if this is indicative of some English rule or just a "fact" of general usage. It reminds me of the difference between por and para in Spanish, though. – Zairja Aug 9 '12 at 21:02
I'm not a native speaker, but I never heard or read "key of something", and I consume quite a lot of english content – Alex Aug 10 '12 at 13:25
up vote 3 down vote accepted

As I stated in comment, keys in the standard sense pair with locks. Copies can be made, but in theory, each lock has only one key that unlocks it. See also:

share|improve this answer
I'd go for the same expression you indicate, that is "key to"; however, the OP indicated "for" as the preposition of his choice, so your last sentence is not entirely suitable. – Paola Aug 9 '12 at 21:44
@Paola I misread it, thank you. – cornbread ninja 麵包忍者 Aug 9 '12 at 21:51

I can see using “key to” when the “to” is part of a verb phrase. “The key to unlock the door is under the mat.” “The key to understanding the problem was remembering PEMDAS.”

If a preposition and a linking verb are used, perhaps “for” is a better choice. "To stay healthy, the key for me is watching my weight."

share|improve this answer
In "the key to understanding the problem", the part after to is a noun phrase, not a verb phrase. To is a preposition there. In "the key to unlock the door", to is part of the infinitive; of course you can call it a verb phrase if you must, but that's unnecessarily misleading. It looks like you opted for the term only to have a convenient (but wrong) hypernym. – RegDwigнt Nov 15 '12 at 19:45

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.