I have just encountered the following phrase:

It is important that each player not know what the other player will do.

Why is it written here "not know" and not "not knows"? Also would it be correct to say "...player does not know..."?

  • 7
    Congratulations, you've just discovered the Subjunctive Mood. (0: For more detail see here: en.wikipedia.org/wiki/Subjunctive_mood - and here - en.wikipedia.org/wiki/English_subjunctive Sep 3, 2014 at 14:05
  • 2
    What @CopperKettle said. But don't despair! Even native speakers find the subjunctive a bit awkward, which is why many if not most of us today would be more likely to say It is important that each player doesn't/does not know what the other player will do. Sep 3, 2014 at 14:40
  • @FumbleFingers I heard that this form is frequent only in American English, is that right?
    – jinawee
    Sep 3, 2014 at 21:46
  • @jinawee: I have a sneaking suspicion that (apart from some orthographic changes introduced by Noah Webster) mainstream American English is more "conservative" than BrE. So it's at least possible this use of the subjunctive isn't dying off as quickly in AmE as it is in BrE. That fact of your example being in the negative also affects usage. If it weren't for the word not, even more people would be happier with "It is important that each player knows what the other player will do" (even though technically, subjunctive know is/was "correct"). Sep 3, 2014 at 22:04
  • ...apropos which, have a look at this NGram, and toggle the corpus between British and American. It does rather suggest you're right, that Americans are somewhat behind Brits in respect of this usage shift. But you probably want to learn the usage of the future, not the past, so I'd advise you to stick with us Brits! Sep 3, 2014 at 22:09

2 Answers 2


This is the Subjunctive Mood. People will avoid using it by rephrasing their sentences all the time without noticing it, many times with an infinitive. In here, one would usually say it like this

It is important for each player not to know what the other player will do.

This site has good information about the subjunctive. On the site there is a list of verbs and phrases that are followed by the subjunctive (I pasted them here in case the link breaks someday).

Verbs followed by the subjunctive: to advise (that) to ask (that) to command (that) to demand (that) to desire (that) to insist (that) to propose (that) to recommend (that) to request (that) to suggest (that) to urge (that)

Source, Language Dynamics

Phrases followed by the subjunctive: It is best (that) It is crucial (that) It is desirable (that) It is essential (that) It is imperative (that) It is important (that) It is recommended (that) It is urgent (that) It is vital (that) It is a good idea (that) It is a bad idea (that)

Source, Language Dynamics

In the subjunctive, the he, she, it form of the verb takes the same verb form as the others, as you noticed in the sentence you saw.

Just keep in mind, like FumbleFingers said in his/her comment above, the subjunctive is not used very often, but it's pretty cool!


I am not a native speaker but I have never had any issues with that. Let me explain the logic behind this phenomenon: We deal with "invisible" modal verb "should" in this kind of sentences. It is important that each player (should) not know what the other player will do. The same logic applies to similar structures: it is necessary that she (should) do it. It is required that he (should) be here at 5 p.m.

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