UK:*UK and possibly other pronunciationsUK and possibly other pronunciations/ˈsəʊ/US:USA pronunciation: IPA and respellingUSA pronuncation: IPA/soʊ/ ,USA pronunciation: respelling(sō)

WordReference Collins English Usage © 2020
So is used in several different ways.
referring back
You can use so after do to refer back to an action that has just been mentioned. For example, instead of saying ‘He crossed the street. As he crossed the street, he whistled’, you say ‘He crossed the street. As he did so, he whistled’.
He went to close the door, falling over as he did so.
A signal which should have turned red failed to do so.
You can use so after if to form a conditional clause. For example, instead of saying ‘Are you hungry? If you are hungry, we can eat’, you say ‘Are you hungry? If so, we can eat’.
Do you enjoy romantic films? If so, you will love this movie.
Have you finished? If so, put your pen down.
You often use so after a reporting verb such as think or expect, especially when you are replying to what someone has said. For example, if someone says ‘Is Alice at home?’, you can say ‘I think so’, meaning ‘I think Alice is at home’.
‘Are you all right?’ – ‘I think so.’
‘Will he be angry?’ – ‘I don’t expect so.'
‘Is it for sale?’ – ‘I believe so.’
The reporting verbs most commonly used with so are believe, expect, hope, say, suppose, tell, and think.
➜ See believe
➜ See expect
➜ See hope
➜ See say
➜ See suppose
➜ See tell
➜ See think
So is also used in a similar way after I'm afraid.
‘Do you think you could lose?’ – ‘I’m afraid so.'
You can also use so to say that something that has just been said about one person or thing is true about another. You put so at the beginning of a clause, followed by be, have, an auxiliary verb, or a modal, and then the subject of the clause.
His shoes are brightly polished; so is his briefcase.
Yasmin laughed, and so did I.
‘You look upset.’ – ‘So would you if you’d done as badly as I have.'
used for emphasis
You can use so to emphasize an adjective. For example, you can say ‘It’s so cold today'.
I've been so busy.
These games are so boring.
However, if the adjective is in front of a noun, use such, not ‘so’. Say, for example, ‘It’s such a cold day today'.
She was so nice.
She was such a nice girl.
The children seemed so happy.
She seemed such a happy woman.
➜ See such
If the adjective comes after the, this, that, these, those, or a possessive, don't use ‘so’ or ‘such’. Don't say, for example ‘It was our first visit to this so old town’. You say ‘It was our first visit to this very old town’.
He had recovered from his very serious illness.
I hope that these very unfortunate people will not be forgotten.
You can also use so to emphasize an adverb.
I sleep so well.
Time seems to have passed so quickly.
‘so...that’ used to mention a result
You use so in front of an adjective to say that something happens because someone or something has a quality to an unusually large extent. After the adjective, use a that-clause.
The crowd was so large that it overflowed the auditorium.
We were so angry we asked to see the manager.
Be careful
Don't use ‘so’ in the second clause. Don't say, for example, ‘We were so angry so we asked to see the manager’.
You can use so in a similar way in front of an adverb.
He dressed so quickly that he put his boots on the wrong feet.
She had fallen down so often that she was covered in mud.
Instead of using so in front of an adjective, you can use such in front of a noun phrase containing the adjective. For example, instead of saying ‘The car was so old that we decided to sell it’, you can say ‘It was such an old car that we decided to sell it’.
The change was so gradual that nobody noticed it.
This can be such a gradual process that you are not aware of it.
You can use so, and so, or so that to introduce the result of a situation that you have just mentioned.
He speaks very little English, so I talked to him through an interpreter.
There was no answer and so I asked again.
My suitcase had been damaged, so that the lid would not close.
‘so that’ in purpose clauses
You also use so that to say that something is done for a particular purpose.
He has to earn money so that he can pay his rent.
so - very - too
So, very, and too can all be used to intensify the meaning of an adjective, an adverb, or a word like much or many.
Very is a simple intensifier, without any other meaning.
The room was very small.
We finished very quickly.
➜ See very
So can suggest an emotion in the speaker, such as pleasure, surprise, or disappointment.
Juan makes me so angry!
Oh, thank you so much!
So can also refer forward to a result clause introduced by that.
The traffic was moving so slowly that he arrived three hours late.
Too suggests an excessive or undesirable amount.
The soup is too salty.
She wears too much make-up.
Too can be used with a to-infinitive or with for to say that a particular result does not or cannot happen.
He was too late to save her.
The water was too cold for swimming.
➜ See too
'so' also found in these entries:

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