A friend of your father

[Sparkita]

Hi! I wonder if someone can help me out. I'm confused as to the correct way of writing this: A friend of your father... or A friend of your father's.
Thank you very much!

[MrPedantic]

Hello Sparkita, welcome to Using English!

Both are fine:

1. I was talking to a friend of your father's last night. He said you were an obnoxious little boy, when you were five years old.

2. Did you say that Tolstoy was a friend of your father?

The construction in #1 is known as the "double genitive". It's a perfectly natural English idiom, and is probably the more common of the two – at least, in ordinary usage.

Sometimes people avoid it in more formal usage; you would be more likely to find the #2 version in (for example) a serious biography.

(To my mind, the version in #1 gives a greater sense of "a circle of friends, of which X is one". But other posters may well disagree!)

All the best,

MrP

[CaRpE_dIeM]

1. I was talking to a friend of your father's last night. He said you were an obnoxious little boy, when you were five years old.

2. Did you say that Tolstoy was a friend of your father?

The construction in #1 is known as the "double genitive". It's a perfectly natural English idiom, and is probably the more common of the two – at least, in ordinary usage.

Hello MrP,

I was taught that instead of "a friend of my father's" we had to use "my father's friend", is there any difference? I mean, can they both be used with any context or is there a rule? I remember that I wrote a similar sentence to "a friend of my father's" and my teacher (well, she is not a native) said it was wrong.

Thanks in advance for your help!