初中英语重难点 ｜ can 与 be able to：一个只管现在，一个横跨所有时态

你家孩子是不是一遇"能 / 会"就只会写 can？可一上考场就现形：将来时"明天能去"为什么不能写 can go？was able to 和 could 到底差在哪？表"成功做到"为什么偏偏不能用 could？

这篇只解决一个问题：把 can 与 be able to，从"都会用 can"升级成"看清时态和场合"。

01 先弄清出处：这讲的是几年级的知识点？

can 表能力是人教版七年级下册 Unit 5 Why do you like pandas? 等单元的核心语法，be able to 的时态扩展（will be able to / has been able to）与 was / were able to 表"过去成功做成"则在八年级下册至九年级逐步加深，是中考单选、完形的高频考点。

适用学段：七年级（can 初学）、八年级（be able to 扩展）、九年级中考冲刺（was able to 区分）均适用。

02 先比较：can 与 be able to 的分工

一句话：can 是情态动词（只管现在，无将来 / 完成时），be able to 是"能"的万能版（各种时态都能用）。

· can（情态动词）：I can swim.（我会游泳。——现在能力）

· be able to（动词短语）：I will be able to swim tomorrow.（明天我就能游泳了。——将来时）

判断口诀：看到将来时（will）和完成时（has / have）要表"能"，一律用 be able to——can 没有这两种时态。

03 深度拆解：七个知识点全掌握

知识点一｜can 作情态动词：表"能力"（现在时，无人称变化）

I can swim very well.（我游泳游得很好。）

She can play the piano.（她会弹钢琴。）

He can speak three languages.（他会说三种语言。）

They can run fast.（他们跑得快。）

My brother can cook delicious food.（我哥哥会做美味的食物。）

We can help you with your homework.（我们能帮你做作业。）

规律：can 是情态动词，表现在的能力；后面接动词原形，无人称和数的变化——He can swim（不是 He cans swim）。

知识点二｜be able to 表"能力"：有人称和时态变化（可替代 can）

She is able to speak English well.（她英语说得很好。——现在时 is able to）

I am able to ride a bike now.（我现在会骑自行车了。——am able to）

They are able to finish the work on time.（他们能按时完成工作。——are able to）

He is able to solve the problem.（他能解出这道题。）

We are able to see the stars at night.（我们晚上能看到星星。）

My sister is able to draw beautiful pictures.（我妹妹会画漂亮的画。）

规律：be able to = can（表能力时），但 be 要随主语和时态变化——am / is / are able to；can 无人称变化，be able to 有。

知识点三｜将来时：will be able to（核心难点——can 没有将来时）

She will be able to go to school next week.（她下周就能上学了。——√）

He will be able to tell you the news tomorrow.（他明天就能告诉你这个消息了。）

They will be able to finish the project by Friday.（他们周五前就能完成这个项目。）

You will be able to see the doctor soon.（你很快就能见到医生了。）

I will be able to drive a car when I am 18.（我 18 岁就能开车了。）

We will be able to visit the museum next month.（我们下个月就能参观博物馆了。）

规律：表将来的"能"，用 will be able to——can 没有将来时，不能说 will can；这是中考单选最爱挖的坑。

知识点四｜完成时：has / have been able to（can 没有完成时）

He has been able to swim since he was five.（他从五岁起就会游泳了。——√）

She has been able to read since the age of four.（她四岁起就会阅读了。）

They have been able to finish the task.（他们已能完成这项任务。）

I have been able to speak English for two years.（我说英语已经两年了。）

My father has been able to walk again after the accident.（事故后我爸爸又能走路了。）

We have been able to solve many problems this term.（这学期我们解决了许多问题。）

规律：现在完成时表"已经能 / 一直能"，用 has / have been able to——can 没有完成时，不能说 have can / has can。

知识点五｜was able to vs could：过去"成功做成" vs 过去"一般能力"（核心难点）

He was able to finish the race.（他成功跑完了比赛。——过去特定场合成功做到 √）

She was able to catch the last bus last night.（她昨晚赶上了末班车。——成功做到）

The firemen were able to save the boy from the fire.（消防员成功从火中救出了男孩。——成功做到）

He could swim when he was five.（他五岁时就会游泳了。——过去一般能力，可用 could）

When I was young, I could run very fast.（我年轻时跑得很快。——过去一般能力）

They could sing English songs at the age of six.（他们六岁就能唱英文歌。——过去一般能力）

规律：表示"过去特定场合成功做成了某事"用 was / were able to（= managed to / succeeded in doing），不用 could；could 只表过去一般的能力（会做，不一定做了）。

口诀："成功做到"用 was able to，"过去会做"用 could。

知识点六｜can 的其他身份：表"许可"和"推测"（be able to 不能）

Can I use your pen?（我可以用你的钢笔吗？——表许可）

You can sit here if you like.（如果你想，可以坐这里。——表许可）

Can I ask you a question?（我可以问你一个问题吗？——表请求）

It can be very cold in winter here.（这里的冬天有时会很冷。——表推测"可能"）

That can't be true.（那不可能是真的。——can't 表否定推测）

Can the news be true?（这消息可能是真的吗？——疑问表推测）

规律：can 还能表"许可 / 请求"（Can I...?）和"推测"（can't 不可能 / Can...be...?）；be able to 只表"能力"，不能表许可和推测。

知识点七｜易错点：四个"要命"的坑

He cans swim.（×）→ He can swim.（√）——can 是情态动词，无人称和数的变化，第三人称单数也不加 s。

She will can come tomorrow.（×）→ She will be able to come tomorrow.（√）——can 没有将来时，将来"能"用 will be able to。

He has can swim since 5.（×）→ He has been able to swim since 5.（√）——can 没有完成时，完成时用 has / have been able to。

I could pass the exam yesterday.（× 表成功做到）→ I was able to pass the exam yesterday.（√）——过去特定场合"成功做到"用 was able to，不用 could。

Can you swim?（√ 你会游泳吗？）vs Are you able to swim?（√ 你会游泳吗？）——表现在能力两者可互换。

He is able to be at home now.（×）→ He can be at home now.（√）——表"推测 / 可能"只能用 can / may，be able to 不表推测。

规律：四个坑分别是——can 无人称变化（不加 s）、can 无将来时（will be able to）、can 无完成时（has been able to）、"成功做到"用 was able to 不用 could。

04 配套练习：10 题精练

一、单项选择（1—8 题）

1. She ___ swim very well. A. can  B. cans  C. is can  D. will can

2. He ___ able to speak English when he was ten. A. is  B. was  C. will be  D. has been

3. They will ___ to finish the work tomorrow. A. can  B. be able  C. able  D. be able to

4. He has ___ able to walk again after the accident. A. be  B. been  C. being  D. is

5. The firemen ___ save the boy from the fire last night. A. could  B. can  C. were able to  D. are able to

6. When I was five, I ___ read. A. could  B. can  C. am able to  D. will be able to

7. — ___ I use your pen? — Sure, here you are. A. Can  B. Am able to  C. Do  D. Are

8. That ___ be true. He is always honest. A. can't  B. must  C. can  D. is able to

二、用 can 或 be able to 的正确形式填空（9—10 题）

9. She ___ (be able to) go to school next week.

10. He ___ (can) swim when he was a child.

05 参考答案与解析

1. A。can 表现在能力，无人称变化，不加 s。

2. B。when he was ten 表过去，be 用 was，was able to。

3. D。will 后面接 be able to，表将来"能"。

4. B。has + been able to，完成时用 been。

5. C。last night 过去特定场合"成功救出"，用 were able to。

6. A。过去一般能力"会读"，用 could。

7. A。表请求 / 许可用 Can I...?。

8. A。can't 表否定推测"不可能"。

9. will be able to。next week 将来时，用 will be able to。

10. could。when he was a child 过去一般能力，用 could。

06 加分考点：三个延伸用法

· 过去"成功做到"的三兄弟：was / were able to = managed to do = succeeded in doing——He was able to escape = He managed to escape = He succeeded in escaping.（他成功逃脱了。）

· could 的委婉请求：Could you help me?（比 Can you help me? 更委婉客气）——注意回答用 can / can't，不用 could。

· be able to 前加情态动词：may be able to / might be able to / should be able to——She may be able to come.（她也许能来。）——can 不能这样叠用。

写在最后

can 与 be able to 不是"都会用 can"，而是"看清时态和场合"：表能力两者通用（I can swim = I am able to swim），但将来时用 will be able to、完成时用 has been able to、"过去成功做到"用 was able to、表许可和推测只能用 can。

你最容易栽在哪个 can / be able to 的坑上？欢迎把错题发到评论区，下期我们继续拆。