When is it correct to create a contraction of words followed by is? For instance is who’s a correct short form of who is?

  • or even "who was"? – Robert Koritnik Mar 18 '11 at 14:30
  • 1
    @Robert: I think "who has" but not "who was" – Henry Apr 29 '12 at 18:58

The word "is" can always be contracted, provided it is not stressed - though this is considered somewhat informal.

So, in informal contexts,

Fred is taller than Jim.

can be shortened to

Fred's taller than Jim.

...it doesn't depend on what word comes before "is". But if the is is emphatic:

Fred is taller than Jim.

then it would be wrong to contract that to

* Fred's taller than Jim.

That is probably fairly obvious - if you are stressing a particular word, it doesn't pay to shorten it. But there are also other situations where the is has the emphasis, for instance

I don't know what it is.

cannot be contracted to

* I don't know what it's.

even though

I don't know what it is doing.

can be reduced to

I don't know what it's doing.

  • psmears, i like your answers ! – n0nChun Mar 18 '11 at 10:09
  • @n0nChun Thank you, it's nice to be appreciated :-) – psmears Mar 18 '11 at 10:44
  • I think in ordinary, non-emphatic speech (but not writing unless it is intending to mimic speech), it's not so much that you "can" contract is, but rather that speakers practically always do. – Neil Coffey Mar 18 '11 at 12:04
  • @psmears, Why can't ""I don't know what it is."" be reduced? – Pacerier May 6 '17 at 6:53
  • @Pacerier: As it says in the answer, you can't contract/reduce "is" when it is stressed. In "I don't know what it is", the word "is" is stressed, so you can't contract it. – psmears May 8 '17 at 13:25

Who's is the correct contraction of who is, in the same way let's is the contraction of let us.

There are no grammatical rules about not using 's as a contraction of is.
In some cases, there could be a confusion between 's used as contraction of is, and 's used as possessive, but the rest of the sentence should clarify which is the exact meaning of the contraction.

Geraldine's back
Barak's thinking

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