How to use"as "
When I read and write English ,one of the most difficult word for me is " as ".
Because " as " has a lot of use .
And the use is all depends.
I try to search sample sentence by English dictionary every time .
But I can't understand enough.
I think " as " is surely convenient , but at same time, it is bother , especially for me !
Please tell me how to use it .