The types and the functions of “so”:

1. so … (that) … so … as to do something to such a great degree:
Don’t look so angry.

2. very; extremely:
I’m so glad to see you.

3. not ~ … (as … ) (used in comparisons) not to the same degree:
I haven’t enjoyed myself so much for a long time.

4. used to show the size, amount or number of something:
The fish was about so big

5. used to refer back to something that has already been mentioned:
I hope so.

6. also:
Times have changed and so have I.

7. used to agree that something is true, especially when you are surprised:
‘There’s another one.’ ‘So there is.’

8. (informal) used, often with a negative, before adjectives and noun phrases emphasize something that you are saying:
That is so not cool.

9. (informal) used, especially by children, to say that what sb says is not the case and the opposite is true:
‘You’re not telling the truth, are you?’ ‘I am so!’

10. used when you are showing somebody how to do something or telling them how something
happened:
So it was that he finally returned home.