This is a two-part question:

1) I have consulted multiple sources and found that 'it isn't' and 'it's not' have little to no semantic difference. If they are pretty much equivalent then for what reason is -

It's not like we didn't try our best

preferred to:

It isn't like we didn't try our best

If they are both correct grammatically why is the first construction much more common and even sound more natural. Is it a matter of placement of emphasis?

2) It is stated in a grammar article that tag question should be in the opposite form to the main question. However, in a case of two negatives yielding a positive like the example above, should the tag question be negation or positive?

  1. It's not like we didn't know what to do, is it?


  1. It's not like we didn't know what to do, isn't it?

Which one obeys the rule, 1 or 2?

Many thanks in advance.

  • 1
    As I can only offer experience-based opinion, I will make a comment instead of an answer. For your first question, isolating the word not adds emphasis; it's not merely a negation, but an emphatic negation. For your second question, insert the implied or immediately after the comma, and you should realize why statement 1 makes sense and statement 2 does not.
    – Davo
    Mar 3, 2017 at 13:52
  • 1
    The tag question should have a 'polarity' (negative v positive) opposite the polarity of the main clause, so 1. is correct: "It's not" → "is it?" Mar 3, 2017 at 14:02

2 Answers 2



The sentences are the same. In fact, the emphasis doesn't make a difference in meaning at all as far as I can tell. The first may sound better simply due to how the sentence flows (I'm not a poet, perhaps someone else can explain better). It could also be due to the fact that it's a more common construction, and thus sounds more "normal".


The tag question has opposite polarity of the main clause, as someone else said. The first sentence is correct.


Both contractions are correct!

  • It is not (formal) ✅

  • It's not ✅

  • It isn't


  • The New Cambridge English Course-2 (p. 79)
  • Cambridge English Prepare! Level 2 Student's Book p.144
  • BBC learning English.


All are contractions forms of "It is not". but, while "it's not" has two syllables, "it isn't" has 3 syllables, which makes it a little bit less easy to use, but still people use it widely.

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