In English, the word "mine" shows possession. "Me" is just referring to yourself as a person. So saying "A friend of mine" shows that they are your friend. You possess a friendship with that person. I hope this helps.

Easier colloquial ways used on the street. You can use in standard formal English also. 1. "A friend of mine" = "my friend" (people say this most often). 2. "My friend, my friends" = say this instead of using the of (a friend of me that is wrong) 3. A friend of my -(friend/brother/sister/mother/father/boss/neighbour/neighbor/grandfather/grandmother/cousin/uncle/aunt/teacher) etc any person that you can say "my + ) 4. A friend of the - (policeman/priest/vicar/rabbi/iman/librarian/landlord/gardener/park-keeper/shopkeeper/milkman/postman/traffic-warden) etc. any person that you would not usually instinctively say "My +) 5. The flexible ones. "a friend of my" / teacher/priest/vicar/rabbi/iman/ etc = people in the friend OF THE list that you could also refer to MY + "A friend of my DOCTOR" would at least in British English be used, where "a friend of MY Doctor" is always used. people always refer to their doctor and speak of them as "MY DOCTOR" you can add My teacher to this list also

This can be tricky to understand since "me" and "mine" are both first person singular pronouns. I'm busy writing an article to explain the difference with examples in more detail - I'll send you the link once I've published. For now, the main difference between these two pronouns is that "mine" denotes possession. And one way for you to remember the difference easily, is to think of the American movie called "Yours, Mine & Ours" - the title contains three possessive pronouns that refer to the children each parent brings into the marriage as well as the children they have together. I hope this helps a bit.

The second one is correct! A friend of mine. :)

a friend of mine is the correct version.