Question

can 和be able to的区别

Answer 1

can和be able to都可以表示能力，它们的区别如下：
一、在用于过去时时，can和be able to的含义不同。
can用于过去时，即could，只表示能力，be able to用于过去时时，可以叙述过去经过一番努力才能完成的事情，如：
I was able to run away, but Tony wasn't.
He was able to get an A in the math exam.
二、be able to的时态较多，在情态动词或助动词后面，只能用be able to。
can只有动词原形和过去式could两种时态，而be able to的时态比较多，如主句为过去时的时候，直接引语里的过去时could要变成had been able to，而将来时要用will be able to，过去有能力，而现在丧失了这个能力，叫做used to be able to。这种情况下，都不能用can来表示。
You will be able to swim soon.
I haven't been able to recall his name.
He said, "I couldn't fix your TV yesterday."
He told me that he hadn't been able to fix my TV the day before.
I used to be able to speak Japanese, but I can't now.

Answer 2

(1) be able to 强调通过努力而获得的能力，而can则强调自身已具有的能力。如：
She can sing the song in English. 她能用英语唱这首歌。
He will be able to sing this song in English in a few minutes, too. 几小时之后，他也能用英语唱这首歌。
(2) be able to 强调一种结果，而can只强调一种可能。如：
Luckily, he was able to escape from the big fire in the end. 幸运的是，他终于逃出了大火。
If he got here a few hours earlier, I could save him. 要是他早几小时来，我还能救他。
(3) be able to 可以有各种时态；而can只有一般现在和一般过去两种时态。如：
I could help you last night, but you didn’t come. 昨天晚上我能帮你，而你又没来。
Can you see it there? 你能看见它在那儿吗？
He is / was / will be able to help you. 他能帮你的忙(from www.yygrammar.com)。
(4) can可用于表示可能性，推测，允许等情况，而be able to通常不这样用。

Answer 3

　　be able to 与can用法区别
　　
　　(1) be able to 强调通过努力而获得的能力，而can则强调自身已具有的能力。如：
　　She can sing the song in English. 她能用英语唱这首歌。
　　He will be able to sing this song in English in a few minutes, too. 几小时之后，他也能用英语唱这首歌。
　　(2) be able to 强调一种结果，而can只强调一种可能。如：
　　Luckily, he was able to escape from the big fire in the end. 幸运的是，他终于逃出了大火。
　　If he got here a few hours earlier, I could save him. 要是他早几小时来，我还能救他。
　　(3) be able to 可以有各种时态；而can只有一般现在和一般过去两种时态。如：
　　I could help you last night, but you didn’t come. 昨天晚上我能帮你，而你又没来。
　　Can you see it there? 你能看见它在那儿吗？
　　He is / was / will be able to help you. 他能帮你的忙
　　(4) can可用于表示可能性，推测，允许等情况，而be able to通常不这样用。