So can act as a substitute for an adjective, adverb, or a whole clause if we don’t want to be overly repetitive:
Richard was enraged at his brother’s stupidity and he had every right to be so. (= to be enraged)
Elon considered the suggestion seriously and Helen even more so. (= even more seriously)
Mike’s going to be there. At least I presume so. (= that he is going to be there)
We often use so instead of a clause after verbs concerned with thinking and speaking:
to imagine, to tell, to be afraid (expressing regret), to appear / to seem, to assume, to believe, to expect, to guess, to hope, to presume, to suppose, to suspect, to think
Karen is not the one who would cheat the system, at least I assume so.
- I’ve heard he’s planning to purchase an apartment in the centre. - I’d imagine so. He’s been wanting to buy one for a few years.
- Will you drop by for a cup of tea? - I think so. It depends on how tired I will be after work.
I found their ideas ridiculous and said so / told them so.
NB! The verb “to tell” requires an indirect object.
We don’t use so after certain verbs:
to accept, to admit, to agree, to be certain, to hear, to know, to promise, to suggest, to be sure, to doubt
- Is there an alternative solution? - I doubt it / that.
- It won’t be so easy for you to find this book. - I know.
I will always be with you, I promise.
In negative sentences, we can use either not or not…so:
- Will there be anything new in the new addition of the book? - It would appear not.
They want to reduce the salary, although they haven’t said so directly.
We can use either not or not…so with to appear, to seem, to suppose:
- I don't suppose he’ll make an exception for you. - No, I don’t suppose so. / No, I suppose not.
We prefer not…so with to believe, to expect, to imagine, to think. Not with these verbs sounds rather formal:
- Will we need to provide a birth certificate? - I don’t think so. (formal: I think not)
We use not with to be afraid (expressing regret), to assume, to guess, to hope, to presume, to suspect:
- You’d better rely on yourself since Fen won’t help you. - No, I guess not.
Let’s compare the use of not (to) and not…so with the verb “to say”:
- Do you have to read everything on the list? - The teacher said not. (= the teacher said we didn’t need to)
- Do you have to read everything on the list? - The teacher said not to. (= the teacher said that we shouldn’t)
- Do you have to read everything from the list? - The teacher didn’t say so. (= the teacher didn’t say that we should read everything, but perhaps we should)
We can use so in a short answer when we want to say that we can see something is true now that we have been told. We can also use so + pronoun + auxiliary verb (to be, can, etc.):
- The dinner is ready. - So it is.
- The guests are here. - So they are.
However, if we already know something, we use “Yes, …” instead of “So…”. Let’s compare:
- Your book has been torn. - So it has. / Yes, it has. I wonder who did it. (= I didn’t know before you told me)
- Your book has been torn. - Yes, it has. It was Jake who did that. (= I knew before you told me)
We can use so in a similar way in short answers with verbs such as to appear (after “it”), to believe, to gather, to hear, to say, to seem, to tell, to understand. However, with these verbs, the pattern implies “I had known before you told me about it”:
- You know, I found this movie quite mediocre. - So I gather (= I knew that), you didn’t look excited while watching it.
