Jim is a 10-year-old boy from Australia. Now he lives in Beijing and we are good friends. He is shorter than I am, but he is stronger than me. He likes sports and he is a great swimmer. He also likes watching cartoons. He often watches Animal World with his sister. Jim helps me with English and he is also good at maths. Jim is the quietest and smartest boy in our class.

short（短的）→ shorter（比较短的） →shortest（最短的）
swim：游泳（动词）→swimmer：游泳者（名词）