I've learned that starting a sentence with a subordinating conjunction such as "if" there must be a dependent and independent clause. So to me the sentence,

If not, we do not need to start its procedure.

is ungrammatical. I'm getting tripped up by the fact "If not," could be a parenthetical phrase.

I was hoping someone would help me differentiate.

Note: The referenced example is found in an ETS dataset "of sentences with ordinal labels for grammaticality." https://github.com/EducationalTestingService/gug-data/blob/master/gug_annotations.tsv

  • Ask yourself: To what does "If not" refer? Compare your sentence to: "If it does [something], we do not need to start its procedure." – P. E. Dant Sep 21 '16 at 1:36
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    Is it ungrammatical, though? Consider: "He must be ready. If not, we do not need to start the procedure." The second sentence refers to the first, but it's still a sentence in its own right. Here's another example containing a sentence that legitimately starts with If not: "If you want this to be an answer, tell me now. If not, remain silent." (Note that "If not" is not parenthetical - you can't throw it away without changing the meaning of the sentence.) – Lawrence Sep 21 '16 at 4:03
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    @Lawrence The sentence is not ungrammatical, but the OP has not provided context to provide a referent for the dependent clause. (By the way, the sentence without the putative parenthetical is entirely grammatical as well!) – P. E. Dant Sep 21 '16 at 7:03
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    @Alw Yes and no. <--- Is that grammatical with no context? – Jim Reynolds Oct 21 '16 at 7:21
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    Evaluate the grammaticality of the sentence: Bananas. Compare to that sentence's grammaticality in Q: By what nickname does J.R.'s team of psychiatrists call him? A: Bananas. – Jim Reynolds Oct 21 '16 at 7:59

If not, we do not need to start its procedure.

This is grammatical, but if not isn't really a parenthetical phrase. If so and if not are special reduced forms in which the pro-forms so and not stand for full finite clauses; so is positive and not is negative.

This is described on pages 757 and 1536 of The Cambridge Grammar of the English Language, where we can find the following examples:

  1. There'll probably be a vacancy in June; if so, we'll let you know.
  2. We may be able to finish tomorrow; if not it will certainly be done by Friday.

In the former example, if so is interpreted as "if there is a vacancy in June", and in the latter example, if not is interpreted as "if we aren't able to finish tomorrow".

In your example, so refers back to a full finite clause from the preceding context. Since you haven't supplied the context, I can't tell you what exactly it is, but you should understand it as standing for a clause.


If not, I think, is kind of a set phrase. It is a shorthand for "if it is not". I suppose there is some type of verbless clause involved (it is a subordinate clause, if clause).

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