(1) be able to 強調(diào)通過努力而獲得的能力,而can則強調(diào)自身已具有的能力.如：

　　She can sing the song in English.她能用英語唱這首歌.

　　He will be able to sing this song in English in a few minutes,too.幾小時之后,他也能用英語唱這首歌.

　　(2) be able to 強調(diào)一種結(jié)果,而can只強調(diào)一種可能.如：

　　Luckily,he was able to escape from the big fire in the end.幸運的是,他終于逃出了大火.

　　If he got here a few hours earlier,I could save him.要是他早幾小時來,我還能救他.

　　(3) be able to 可以有各種時態(tài)；而can只有一般現(xiàn)在和一般過去兩種時態(tài).如：

　　I could help you last night,but you didn’t come.昨天晚上我能幫你,而你又沒來.

　　Can you see it there?你能看見它在那兒嗎?

　　He is / was / will be able to help you.他能幫你的忙

　　Will you be able to camera the lecture tomorrow?你明天能把講座錄下來嗎?

　　I'm sorry I haven't been able to answer your letter in time.真對不起我沒能及時給你回信.

　　Ps:指過去某時或某個時刻設(shè)法做成某事,不用could,而用waswere able to.

　　I talked with her for a long time,and eventually I was able to make her believe me.我談了很久,最終還是使她相信了我的話.

　　(4) can可用于表示可能性,推測,允許等情況,而be able to通常不這樣用.

　　You are able to use my pen.(誤)

　　You can use my pen.(正)

　�。�5） can有被動語態(tài),主語為人或物皆可,而be able to只接不定式的主動形式,不接表示被動的不定式,也不可用無生命的名詞作主語.例如：

　　The work is able to be done by him.（誤）

　　He is able to do the work.（正）