1. A and B both are very good;

  2. A and B are both very good.

  3. Both A and B are very good.

  4. Both of A and B are very good.

Are there subtle differences between the four sentences above?

  • 4
    I don't think you would use "of" except with a pronoun, e.g. "Both of them are very good".
    – augurar
    Commented Mar 6, 2014 at 3:31
  • @augurar: I think that's right. The other ones (1-3) are natural results of quantifier syntax. Commented Mar 6, 2014 at 3:53
  • 3
    @augurar: You'd use it with a plural noun as well. Eg: "Both of the pies are very good." But yeah, "both of A and B" sounds rather odd to me.
    – cHao
    Commented Mar 6, 2014 at 3:55

2 Answers 2


"Subtle differences?" Hmmmm.

Well, there are some simple differences; dunno how subtle they are. Depends.

I agree with @augurar that (4) is ungrammatical, except for unstressed them.
That leaves (rearranging the order a little to show the Q-float direction of both):

  1. Both A and B are very good.
  2. A and B both are very good.
  3. A and B are both very good.

These all mean the same thing.

And here's a couple more sentences that these all come from, via conjunction reduction:

  • A is very good.
  • B is very good.

(or perhaps I should say "that all these come from", because that's Q-Float, too.)

Here's what's going on.

First, both means *all two;
  that is, both has the same syntactic pattern as
  all (integer) X, which only occurs with X > 2
  -- all three of them, all 27 of them, both/all of them.

Second, both and all (and some, each, any, few, and quite a few more) are quantifiers.
Quantifiers are special words that normally modify noun phrases (as in [1.] above).

Third, in English there is a rule called "Quantifier-Float" that allows some (but by no means all) quantifiers -- both or all in this case -- to detach themselves from the noun phrase that they bind, and float away to an adverb niche in the verb phrase. Without, naturally, changing meaning.

That's what happened to [2.] and [3.] above; those are the two available adverb niches in that verb phrase:  either right before the first auxiliary verb -- are -- or right after it.

That's all, really.

  • 1
    Float is, at least sometimes, used to shift focus, and thus the semantics.
    – Kris
    Commented Mar 6, 2014 at 4:35
  • Can do. But that's not syntax; that's pragmatics. At least. Commented Mar 6, 2014 at 4:39
  • 1
    You might also have mentioned "A and B are good". Kind of the elephant in the room here. "Both" is redundant here, but it can emphasize. It can also clarify, if the sentence is more complex (as @JohnLawler points out). And then there is "Each of A and B is good". It means the same thing in general, but it emphasizes that they are each individually good. (Whereas "both" can sometimes suggest that they share a property together, without necessarily each enjoying it individually.)
    – Drew
    Commented Mar 6, 2014 at 6:38
  • 1
    There are two elephants, which I mentioned: A is very good and B is very good. Conjoin them with and and you can do various kinds of conjunction reduction on it (check the link). A and B are very good is one such product. Commented Mar 6, 2014 at 15:03
  • A and B both are very good. --> both is parenthetical, = "A and B, both, are very good."

  • A and B are both very good. --> fine

  • Both A and B are very good. --> A and B is parenthetical, = "Both, A and B, are very good."

  • Both of A and B are very good. --> No parenthetical. A and B = "them"

Yes, there's a distinct difference in meaning, the focus, that shifts between 'A and B', 'both' and 'very good': use as needed.

  • I saw Prof. JL's answer after posting mine.
    – Kris
    Commented Mar 6, 2014 at 4:37

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