The moon rotates itself but it does so very slowly.

In this sentence, I wanted to know the usage of so. So means 'very' or 'rotates itself'?

  • 3
    A very short answer: you can think of "so" in this context as just meaning "that", or "that thing".
    – stangdon
    May 6, 2016 at 0:00
  • 1
    Nice question. These are things I don't think about as a native speaker. It's always good to learn what you take for granted.
    – ktm5124
    May 6, 2016 at 16:31

2 Answers 2


In you example, so refers to the subject of the sentence, the moon's rotation, it's a placeholder

The moon rotates itself but it does so very slowly
The moon itself rotates but its rotation is very slow

I think so
this is what I think

If you say so
if that is what you are really saying

If it wasn't so
If it wasn't the way it is

  • I might have paraphrased the original like this: The moon itself rotates but it rotates very slowly. The "does so" allows the writer to avoid the repeating the word rotates two times so closely together in the same sentence. (Such repetition is not necessarily problematic, and it's certainly not a grammatical error, but it's nice to have a way to avoid that repetition if the writer wants to do so.)
    – J.R.
    May 6, 2016 at 9:20

So is used as an adverb and doesn't refer to the subject of the sentence. It usually refers back to something mentioned before. It is not a placeholder as it has the following meanings defined in Oxford Online Dictionary.

(1) That is the case: ‘Has somebody called an ambulance?’ ‘I believe so

(2) The truth: I hear that you’re a writer—is that so?

(3) Similarly; and also: times have changed and so have I

(4) Expressing agreement: ‘There’s another one.’ ‘So there is.’

Example sentences above mean:

(1) I believe somebody called an ambulance.

(2) Is that true that you're a writer?

(3) I have also changed as times have changed.

(4) Yes, there is another one.

As you can see, the adverb so functions mainly to avoid repetition of a word or words that were previously mentioned.

Your example sentence will be

The moon rotates itself but it (the moon) rotates itself very slowly.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .