1.表示“有能力的”、“能干的”,可用作表語(yǔ)或定語(yǔ).如：
He is an able manager.他是位有能力的經(jīng)理.
He is old but still able.他雖年老,但仍有很能干.
2.用于 be able to do sth(能或會(huì)做做某事).如：
He is able to speak English.他會(huì)說(shuō)英語(yǔ).
Everyone here is able to type.這兒的每一個(gè)人都會(huì)打字.
He will be able to get about in a week or two.再過(guò)一兩個(gè)星期左右他就能走動(dòng)了.
He studied hard and was able to pass his examinations.他學(xué)習(xí)很努力,所以考試及了格.
注：be able to 不僅有多種時(shí)態(tài)形式(通常不用于進(jìn)行時(shí)或與 be going to 連用),而且還可以與某些情態(tài)動(dòng)詞連用(通常不與 can 連用),甚至還可以有非謂語(yǔ)形式.如：
Since his accident he hasn’t been able to leave the house.自出事之后,他一直未能離開(kāi)家.
You might be able to persuade him.你也許能夠說(shuō)服他.
I hope to be able to do the work.我希望能干得了這項(xiàng)工作.
I regret not being able to help her.我很遺憾未能幫助她.
3.able 的比較級(jí)和最高級(jí)通常是 abler 和 ablest,也可以是 more able 和 most able,有時(shí)還可用 better able和best able.如：
You are better able to do it than I (am).你比我更有能力做這件事.
She’s the person best able to cope.她是個(gè)最能妥善處理問(wèn)題的人.
4.若要加強(qiáng)語(yǔ)氣,其前除可very,quite,perfectly等修飾外,有時(shí)還可用well修飾.如：
He is quite [well] able to take care of himself.他完全有能力照顧自己.
He’s a very able student; he’s just too lazy.他是個(gè)很有能力的學(xué)生,只是太懶了.
若受just,only just修飾,則表示“只能”“僅能”.如：
I was just able to make out a dark figure in the distance.我只能看見(jiàn)遠(yuǎn)處有個(gè)黑影.
5.able的反義詞是unable(不能的,不是disable,后者是動(dòng)詞,其意為“使殘廢”“使無(wú)能力”.比較：
They were unable to reach a decision.他們沒(méi)法做出決定.
Now that he was disabled,his house had become a prison to him.因?yàn)樗麣垙U了,他的房子就成了他的牢籠.