The usage of possessive case in English
Which one is correct: "he is a friend of John" or "he is a friend of John's"?

Question

Answer

"He is a friend of John's" is better.

(Though I disagree with Louri - "He is John's friend" does not mean that he is John's only friend.)

Answer

Hello,

'He is a friend of John's' would be correct, or more naturally 'He is John's friend'.

I hope that helps,

Christine

Answer

He is a friend of John's. 
(One of his friends)
He is John's friend.
(Probably the only friend) 
"He is a friend of John" is incorrect.