[误] He is a friend of my father.

[正] He is a friend of my father\'s.

注：名词前面的属格，可代定冠词用，如 my brother\'s wife=the wife of my brother. 又 my brother\'s friends=(all) the friends of my brother. 如果不是指某一个特定的人或几个人时，则须用不定冠词 (a),那是不能用属格来代替的，即是用了属格，还得有不定冠词，但我们又不能说 my brother\'s a friend. 或 a my brother\'s friend，所以只好说 a friend of my brother\'s. 这种表现法所含有的意味是 a friend (that is) my brother\'s 或 one of my brother\'s friends. 这便是英语的双重属格的由来。