I believe the negative of a sentence, in which an infinitive is used, is made in two different ways.

For example, "I know what to say." can be negated as follows;

  1. I know what not to say.
  2. I don’t know what to say.

However, I often come across the swapped version of "not to" as follows;

  1. I know what to not say.

Other examples follow;

  • Tom had enough sense to not go out by himself after dark.
  • I want you to not go to Boston with Tom.
  • Why did you decide to not go to Boston with Tom?

Grammarly finds the third way to be fine.

Google Books Ngram Viewer prefers not to over to not in general.

I need to know if the third way of negating an infinitive-sentence is grammatical. Please, explain!

  • I found the similar question here: english.stackexchange.com/questions/23152/… – Zeeshan Ali Jan 29 '19 at 6:01
  • The traditional idiom, placing the negation before the marker (I soon learned not to provoke her) or with verbs of desire, negating the finite verb (I don't want to see you anymore) remains easy and natural, and is still overwhelmingly the more common construction. Some argue that the two forms have different meanings, while others see a grammatical difference, but most speakers do not make such a distinction. Ref: en.wikipedia.org/wiki/Split_infinitive#Current_views – Zeeshan Ali Feb 6 '19 at 6:47
  • In an example drawn from the British National Corpus the use of to not be against not to be is only 0.35% (from a total of 3121 sampled usages). Ref: en.wikipedia.org/wiki/Split_infinitive#Current_views – Zeeshan Ali Feb 6 '19 at 6:48
  • When you often come across the swapped version of "not to", can you not cite where you found those examples? If they come up "often" where are some others? "I know what to not say" will always be wrong "Tom had enough sense to not go out by himself after dark…" is questionable, and should prolly be "… not to go…" "I want you to not go to Boston with Tom" isn't unintelligible, but it should be "I want you not to…"; more likely, "I don't want you to…" "Why did you decide to not go to Boston with Tom?" should be "Why did you decide not to go to Boston with Tom?" – Robbie Goodwin Jun 3 '20 at 0:44

First of all "I don't know what to say" and "I know what not to say" mean different things. "I don't know what to say" means "It's not true that I know what to say". "I know what to say" means "There are things that I know I shouldn't say".

As to your question, "to not say" is known as "split infinitive". The "to say" phrase is called the "full infinitive", and putting words between "to" and "say" is known as "splitting the infinitive. There are some who say that infinitives "shouldn't" be split. However, this rule based more on an attachment to Latin (in which infinitives are a single word, and thus it is impossible to split an infinitive), rather than actual grammar. There is nothing ungrammatical about split infinitive, and they are arguably more logical.


There isn't any real difference in meaning between "not to [verb]" and "to not [verb]". The second choice sounds clunky and isn't considered grammatical.

Certainly English speakers do use that construction sometimes, especially if they feel, in the moment of speaking, that it somehow fits the exact nuance they are trying to express, or if the words just come out spoken in the order they were thought.

But if you see "I want you to not go to Boston with Tom.", for example, on a multiple choice exam, ... don't choose it. It's not right.

  • Ie "to not"+infinitive is often informally used, however, it is not grammatical, you mean? – Zeeshan Ali Jan 28 '19 at 7:09
  • Which is more commonly used even in informal conversations, verb+“to not”+infinitive OR verb+“not to”+infinitive? ^^ – Zeeshan Ali Jan 28 '19 at 7:10
  • I think "not to infinitive" is a lot more common than "to not infinitive". The latter sounds strange to my ears unless there is some unique situation, or a person is using it for a reason to make some kind of special point. Silly example: "To do the funky-chicken dance is difficult; to not laugh while doing the funky-chicken dance is impossible." There is no reason you couldn't say it correctly: "... Not to laugh while ..." But the parallel construction sounds cool. Clunky though, and not quite right. – Lorel C. Jan 28 '19 at 7:28
  • I am a bit confused, are the sentences (with "to not") that I mentioned in the question even informally usable/acceptable? I.o.w. could one speak those sentences that way? – Zeeshan Ali Jan 28 '19 at 10:54
  • Could/can one casually speak that way that kind of phrases? – Zeeshan Ali Jan 28 '19 at 11:55

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