be good at，意思是擅长干某事。

I am good at playing soccer.我在踢足球方面很擅长；He is good at swimming.他很擅长游泳；My mother is good at cooking.我妈妈擅长烹调；She is good at singing,she is a good singer.她唱歌很好，是一位很棒的歌唱家；My brother is good at learning.我哥哥学习很好。