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difference between "I know him" and "I know who he is"
Both mean pretty much the same thing, but "I know who he is" could also mean, "I have heard of him, or about him; I don't know him as a friend or as an acquaintance.
Structure
I know him: Subject + Verb + Object pronoun
I know who he is: Subject + Verb + Object clause
differeence? 
Linear Mode
