In the following example: I like cakes. So do I.

What word type is "so" taking the role of? Verb, adverb?

I understand that there is some ellipsis happening and the sentences could be re-written:

I like cakes. So do I like cakes.

Apologies if this is a very basic question, but I appreciate your help.

  • 2
    See also english.stackexchange.com/questions/19394/is-so-a-pronoun and english.stackexchange.com/questions/19362/… . 'so' is very complicated, it could be considered a pronoun or an adverb (but usually just an adverb).
    – Mitch
    Commented Jan 11, 2016 at 22:59
  • What @Mitch said. Which effectively means "It's a matter of opinion", and I honestly don't see how such a rarefied discussion can usefully help an OP who presents I like cakes. So do I like cakes. as an "example usage". Commented Jan 11, 2016 at 23:14
  • To @FumbleFinger's point, "so do I like cakes" is not grammatical. I don't see any way to permits those five words or add any to make it so.
    – Mitch
    Commented Jan 11, 2016 at 23:55
  • 1
    It's a little word that certainly punches above its weight!
    – Dan
    Commented Jan 12, 2016 at 0:52
  • How can "so" be a verb?? Can you say: I so, you so, he soes? By the way, every dictionary would give you the label adverb. But of course, not the structure of the formula. I would have explained it in a different way, but StoneyB's is better. Actually it is excellent.
    – rogermue
    Commented Jan 12, 2016 at 10:17

5 Answers 5


So Aux NP -- as in so do I, so are you, so has Mr. Smith -- is a formulaic tag construction
that indicates a deletion, and must be preceded by a clause containing the deleted material.

  • You believe that he lost the race, and so do I.
  • She's an idiot, and so are you.
  • I've been there frequently, and so has Mr. Smith.

In the first sentence, so replaces 'believe that he lost the race';
in the second, it replaces 'an idiot';
and in the third it replaces 'been there frequently'.

The order of the Aux and the so is reversed in this construction, the way it is in a tag question.
Normally so would follow the Aux, as it does in

  • I've always wanted to fill out my own tax forms, but I've never done so.
    Here so replaces 'fill out my own tax forms'

All of these constituents that so replaces are Verb Phrases (VPs).
If a pronoun like it can replace a noun,
and a pro-verb like do can replace a verb,
then the proper term for so is a pro-VP.

  • John, although in these cases do appears to behave like an Aux, it can also co-occur with other Auxes and in fact (more importantly I think) with Aux do itself: I didn't do so. (not *I didn't so) So in these cases it's harder to say it's really an Aux (certainly it's not the same Aux of do support, which makes it harder to say that so itself is a pro-VP.
    – Alan Munn
    Commented Jan 12, 2016 at 4:44
  • @AlanMunn: That's a different form of do, called Action do; it participates in a lot of specialized action constructions, like do dishes/laundry, do damage, do a lot, etc. There's also emphatic do, as in I do love you. Act do is a small verb, the other ones are auxiliary verbs. Commented May 16, 2021 at 18:46

It's whatever your particular grammatical sect calls the word which introduces the back half of a comparative construction:

[As you do,] so do I.

Just like "As Maine goes, so goes the nation".


It's a pronoun of some sort. The exact syntactic category of it is not so obvious, but it's very unlikely to be an adverb.

do so as a whole is a pro-verb-phrase, with do taking the place of the verb and so taking the place of its object. We can see this when we ask questions about verb phrases. The question word that combines with do is what not how, which is what you would expect if so were an adverb. [Note that (2) has an irrelevant grammatical interpretation in which do means "fare" or the like, but this do is not the pro-verb do.]

  1. What did John do?
  2. *How did John do? (≠ 1)

So can never appear conjoined with other adverbs:

  1. John solved the the problem quickly and carefully.
  2. John solved the problem quickly -> *Bill did so and sloppily

So can never be intervened by a sentence adverb, which is a sign of a direct object (thanks to Greg Lee for reminding me of this test.)

  1. *John solved willingly the problem.
  2. John solved the problem willingly
  3. *Bill did willingly so.
  4. Bill did so willingly.

So the conclusion is that so is a pronoun of sorts that stands in for any category that could be the complement of the verb that do substitutes for.


It’s an adverb.

In this context, so means something similar to “equally; in the same way; to the same extent”:

He likes cakes; so do I.

He likes cakes; I like them as much as he does.


It's an adverb, modifying (expanding) "do." It's really an abbreviation of "also" when used this way, although I don't have an etymology reference to cite.

Rearrange the sentence and you'll see its function: "I do also."

  • 1
    In fact it's the other way around, etymologically: also began as all + swa, "entirely so". (And eventually alswa wore down to modern as.) Commented Jan 11, 2016 at 22:27
  • 1
    I don’t think it means the same as “also”. “So” in this context means something like “equally; in the same way; to the same extent”. “Also”, by contrast, would mean something like “additionally; in addition to that”.
    – Timwi
    Commented Jan 11, 2016 at 22:36
  • @StonyB - "all+so" is parallel to German "genau so" oder "ebensio".
    – rogermue
    Commented Jan 12, 2016 at 10:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.