Learn English – “A and B both are” vs. “A and B are both” vs. “Both A and B are” vs. “Both of A and B are”

differencesmeaningsemantics

  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?

Best Answer

"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.

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