Are either of the following sentences grammatically correct?

We know what each other are doing


We know what each other is doing

Neither of them sounds right to me, but surely one of them must be, depending on whether 'each other' functions as a singular or plural? Of course there are workarounds like "Each of us knows what the other is doing", but is it possible to keep the words "each other" together in such a sentence?

  • 2
    I agree that neither sounds right—which is exactly why neither is grammatical. Each other cannot function as the subject of a finite verb in my idiolect of English; I would have no other option than to rephrase to “We each know what the other is doing”. Note that this is also much closer to how the phrase each other originated to begin with (and how it’s still used in some other languages, like French). Sep 17, 2015 at 23:08
  • 2
    Each and other are both determined NPs, and they're singular. What you mean to say is Each of us knows what the other is doing. Putting them together is not necessary, though it is common. BTW, the term for each other is Reciprocal Pronoun; it's a sort of a generalization of Reflexive Pronoun, and it shows up with them sometimes (like Each man considers the other to be superior to himself). Sep 17, 2015 at 23:54
  • Related.
    – tchrist
    Jun 11, 2023 at 23:45

5 Answers 5


If you notice that each other, while idiomatic, is not unbreakable, it begins to come clear.

The reciprocal phrase each other can be separated into one determiner binding something in the subject (each, each one), and one determiner binding something in the object (other, the other), viz:

  • Each (one) of us knows what the other (one (of us)) is doing. (dual)
  • Each (one) of us knows what the others/other ones are doing. (plural)

And some of these quantifiers may be floated to pre-verbal position:

  • We each know what the other (one) is doing. (dual)
  • We each know what the others/other ones are doing. (plural)

From this it's easy to see how each and other hook up:

  • Each of us knows the other.
  • We each know the other.
  • We know each other.

But that doesn't resolve the number problem that comes from having two determiners potentially conflicting. So both

  • *We know what each other is doing. and
  • *We know what each other are doing.

feel wrong.

Of course, there are other quantifiers that specify more precisely,
especially when they're separated, viz:

  • We both know what the other is doing. (dual)
  • We all know what the others are doing. (plural)
  • Why doesn't the same problem arise with we know each other's schedule(s) then (or does it?)
    – user339660
    May 13, 2019 at 20:33
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    @Minty I suspect each other has been univerbated enough to be allowed to function as possessor, but the reciprocality of it makes it semantically impossible as subject. This is the same in other Germanic languages that have univerbated reciprocals: Da. hinanden, Sw. varann/varandra, etc., are happy to be possessors, but cannot be subjects. In fact, I don’t know of any language where a reciprocal can act as subject. May 13, 2019 at 22:15
  • @JanusBahsJacquet Yes, but why, if the basic problem is that the compound is trying to be singular and plural at the same time? Anyway, I'm not sure each other is trying to function as subject. I realise it's in subject position, but I think the each is still trying to reach back to the matrix subject. Its function is to specify that the members of a subject group are to be regarded as having distinct relationships with the verb, I think, which is why we can say we each ate our ice-cream even though more than one ice-cream got eaten.
    – user339660
    May 14, 2019 at 10:27
  • I think the problem with OP's sentences is that the each cannot get past the what so as to hook up with the matrix subject. The same would happen with that in we know that each other is reliable. I'm interested in the number conflict idea but at the moment it seems to me that the numbers don't conflict because one applies to the subject and one to the object.
    – user339660
    May 14, 2019 at 10:30
  • The point of saying that each member of the subject group has a distinct relationship with the verb is normally to highlight that they don't also have the same relationship (it is a several relationship only, not a joint and several relationship). That's why, in the Q that seems to have prompted this new answer about singular and plural, each hiker climbed a hill implies that the hikers were not together, meaning that there's no reason to assume it was the same hill (as in the Q in the survey).
    – user339660
    May 14, 2019 at 10:38

"Each other" refers to a singular subject, just like "one another" does. Notice "each" and "one" are singular; so are "other" (an other v. others) and "another" (which is like a contraction or compression of "an other").

Another way to think of it is: "we know what each other is doing" means "I know what he is doing and he knows what I am doing"...all singular.

  • 1
    Great, thanks. Does this mean "we know what each other is doing" is grammatically correct? Sep 17, 2015 at 21:28
  • 1
    We know what the other is doing would be correct.
    – Justine
    Sep 17, 2015 at 23:31
  • It may be grammatical to you, but it certainly is not to me, regardless of verb agreement. The first sentence in this answer is untrue in my English, because each other (and one another and all other possible reciprocals) does not refer to any kind of subject at all. Reciprocals simply cannot function as subjects. Sentences like these are embedded questions, but unembedding the question here yields, “What is/are each other doing?” – which I hope you agree is quite impossible. May 13, 2019 at 22:20

No, neither needs to be correct because there is a problem of verb agreement. "We" means you and I (inclusively, anyway), so instead of "is doing", you'd need "are doing" for "you" and "am doing" for "I". There is no such problem with "They know what each other is doing" (which, however, still seems a bit odd).

  • "We know" is the independent clause. There is no problem of verb agreement. There would be a problem if it were written "we knows."
    – Justine
    Sep 17, 2015 at 22:32
  • The sentence might be improved by writing: "we know what the other is doing"; nevertheless, "each other" is singular.
    – Justine
    Sep 17, 2015 at 22:36
  • @Justine, Whether there is a problem of verb agreement depends on the order of application of the verb agreement rule and the rule that introduces "each other". So you don't know that there is no problem.
    – Greg Lee
    Sep 17, 2015 at 22:37
  • However I rephrase the sentence, each other takes "is"; "we" does not.
    – Justine
    Sep 17, 2015 at 22:44
  • @Justine, If you begin with "I know what you are doing, and you know what I am doing", there is no apparent way to get to a version with "is doing". But if you begin with "He knows what she is doing, and she knows what he is doing" you can get to "... each other is doing" without the difficulty of rationalizing "are" and "am" somehow to get "is". That's the difference.
    – Greg Lee
    Sep 17, 2015 at 23:14

I would typically phrase something like this as, "We each know what the other is doing." Otherwise, your verb-subject agreement is off. "Is" is singular and we is plural. By adding "each," it becomes the subject associated with the verb. Like, "We each took a cookie from the jar."

Apologies for my typo... I had "know" rather than "is." My fault.

  • Actually, "know" is plural (they know) and "knows" is singular (he knows).
    – Davo
    May 13, 2019 at 18:53
  • Thank you for pointing out my typo. My fingers took off without my brain.
    – MissAJF
    May 13, 2019 at 18:56

It is not grammatically correct to use it like "each other have gotten _____" because this usually functions as a plural, as in "we would help each other out".

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