I wrote some instructions for a friend today, asking them to check something, and then act differently depending on the result:

It should be spinning when it's on. If it isn't then check the batteries. If it is then replace the frobulator.

I used the contraction "it's" for the first sentence to replace "it is".

I didn't use the contraction for the second because I chose to contract "is not" to "isn't". However I could have chosen the opposite: "If it's not check the batteries" would have been fine.

However, the third sentence doesn't sound right if I contract "it is". "If it's then replace the frobulator" seems incorrect.

Is there a rule that explains why "it is" shouldn't be contracted in this case, or am I wrong, and that contraction would be fine in that last sentence?

  • 2
    A related question which I do not know the answer to is whether the other contraction of it is is acceptable. Is "if 'tis, then..." good grammar? It seems plausible. – Eric Lippert Jun 21 '14 at 7:22
  • @Eric Lippert it seems to follow the description: since is in if'tis is there in its entirety at the end of the verb phrase. But wow I didn't know Tis was making a comeback. But I notice a lot of people writing If tis to mean If this. Or maybe that's another construction. – user6951 Jun 22 '14 at 8:51

From The Cambridge Grammar of the English Language, p.1614:

Prepositions, auxiliaries, and infinitival to are stressed when they are the sole or final element in a phrase-level constituent, a PP or VP [preposition phrase or verb phrase].

Note that be is always an auxiliary verb. In your example, is is an auxiliary at the end of a verb phrase:

1a. If it is ___ then replace the frobulator.
1b. *If it's ___ then replace the frobulator.   ← ungrammatical

If we added the ellipted word spinning back in, it would no longer be at the end of the phrase, and it would be possible to contract it:

2a. If it is spinning then replace the frobulator.
2b. If it's spinning then replace the frobulator.

This is the same reason you can't reduce it is to it's at the end of a sentence. Is needs to bear stress, so it can't be reduced to clitic form (can't be contracted).

In this answer, the * symbol means that a sentence is ungrammatical.

  • In: "whose coming with us?" "I am" the word am is NOT stressed - at all. As it currently stands this post is very misleading. :( – Araucaria - Not here any more. Dec 19 '14 at 14:52
  • 1
    The problem as things stand is that the post seems to be confusing strong forms with stressed words. Auxiliaries have to take their strong forms if they are stressed - or - if they are taking code. A strong form does not entail a syllable being stressed. The two things are entirely different. – Araucaria - Not here any more. Dec 19 '14 at 14:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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