两者都可表示“发现”，有时可换用 (discover 更正式)。如：
I discovered [found] an unopened letter in the drawer. 我在抽屉里发现有一封未启开的信。
He discovered [found] the whole story was a lie. 他发现整个故事是一个谎言。
He discovered [found] her sitting near the fire. 他发现她坐在炉火边。
She discovered [found] that he was excited. 她发现他很激动。
但是，若要表示第一次发现以前没有人知道的东西、地方、事实等，则用 discover。如：
Columbus discovered the New World. 哥伦布发现了新大陆。
Penicillin was discovered by Alexander Fleming. 盘尼西林是亚历山大·弗来明发现的。
Modern astronomers have discovered 100 million such galaxies. 现代天文学家发现了一亿个这样的星系。