外公的英语是 "grandfather"，来源是英语中 "grand" 的意思是 "祖父"，"father" 的意思是 "父亲"。
例句：
My grandfather is a retired teacher. (我的外公是一位退休的老师。)
I always enjoy spending time with my grandfather. (我总是喜欢和我的外公在一起。)
My grandfather taught me how to fish. (我的外公教我怎么钓鱼。)
My grandfather always tell me stories when I was a kid. (我小时候，外公经常给我讲故事。)