The subject of this thread was pre-discussed in another thread. But the original question in that thread was poorly worded, so I had to start a new thread.
My question has to do with a mysterious class of noun phrases formed by appending a prepositional post modifier to a main noun, like:

[main noun] [prepositional modifier]

Examples include:

an obligation to his friends
a commitment to excellence
a key to the front door
an answer to that question
an assistant to the manager

From these noun phrases complete sentences could be formed by inserting a proper form of "be" between the main noun and preposition modifier, with or without a slight modification of the main noun by replacing the indefinite particle with a definite particle, demonstrative, or possessive:

His obligation is to his friends.
His commitment is to excellence.
The key is to the front door.
This answer is to that question.
This assistant is to the manager.

For some reason, some of the above complete sentences are not good English according to some native speakers. Why is that?

  • I think you've got the right basic idea, but the verbs could use a little tweaking in a few cases, especially the last one, where "assistant" as a job title doesn't strongly imply a relationship to one who receives assistance.
    – wordsmythe
    Commented Jul 17, 2014 at 19:41

1 Answer 1


Your final examples are generally fine, but they are contextual. They require a specific situation for them to sound natural or make sense. The "X is to Y" structure is an uncommon form, usually used for contrast or for emphasis. So:

His obligation is to his friends

is fine, if you're discussing what he's going to do or how he considers his responsibilities: "Will he stop looking for his friend's lost wallet? Or will he go chat up that woman? He won't stop looking; his obligation is to his friends."


This answer is to that question.

That makes sense, as a response to a previous comment like "I don't understand why this answer doesn't seem to relate to Question 4..." "Oh, well this answer is to that question" (along with a gesture indicating Question 5).

Without context, this kind of emphasis is unexpected and confusing. It's not ungrammatical; it's just semantically unclear. (Although there might be a more natural way to say most of what these sentences would communicate.)

The only sentence I have a real problem with is "This assistant is to the manager"--it seems very unlikely to me that you can find a context in which you would have to stress that this person only assists the manager, while others assist other people; and it's also just kind of weird to talk about people like interchangeable objects.

  • So whether the "X is to Y" structure is acceptable is just a matter of guessing?
    – meatie
    Commented Jul 18, 2014 at 4:32
  • It's not guessing (though it might seem like it if you're learning in a vacuum). It's about whether what you are saying makes sense in the situation. The structure will be most acceptable if you are correcting a confusion or emphasizing one choice over another. It's not a commonly used structure, and the usual rule applies: when in doubt, look for native-speaker example uses if you really want to understand it.
    – Tiercelet
    Commented Jul 18, 2014 at 15:25

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