Summary of Modal Verbs Can, May, and Must for Grade 8 English

Grade 8 English

Summary of Modal Verbs Can, May, Must

Point 1: Usage of modal verbs such as can, may, must in declarative sentences:

1. Usage of can:

(1) Indicates ability, permission, or possibility. When indicating ability, it is generally translated as “can” or “be able to”, meaning having a certain capability, especially an inherent ability. For example: She can swim fast, but I can’t. (她能游得很快，但我不能。)

I can see with my eyes. (我用眼睛看。) “Could” is the past tense of “can”, indicating past ability.

“Be able to do something” often refers to achieving something after effort, time, and labor. “Is/am/are able to do something” and “was/were able to do something”.

(2) Indicates permission, often used in spoken language. For example: You can use my dictionary. (你可以用我的字典。)

(3) Indicates conjecture or possibility, meaning “may”, often used in negative and interrogative sentences; at this time, “can’t” translates to “impossible”.

For example: Can the news be true? (这个消息会是真的吗？)—Can it be our teacher? (那个人有可能是我们老师吗？)—No, it can’t be our teacher. He is on a visit to the Great Wall. (不可能。咱们老师正在游览长城呢。)

[Example]—I think Miss Gao must be in the library. She said she would go there. —No. She __be there, I have just been there. A.can’t B.mustn’t C.needn’t D.wouldn’t

[Analysis] According to the following text “I just went there”, it should be “impossible”, so “can’t” indicates conjecture. [Answer] A

Usage of could:

(1) Past tense of “can”, meaning “could”, indicating past ability. For example: He could write poems when he was 10. (他十岁时就会写诗。)

(2) In interrogative sentences, “could” indicates a polite tone, without carrying the meaning of past tense. For example: Could you give me a hand? (你能帮我个忙吗？)—Could I use your pen? (我能用一下你的钢笔吗?) —Yes, you can. (可以。) (When asking with “could”, do not answer with “could”).

2. Usage of may:

(1) Indicates request or permission, more formal than “can”. For example: May I borrow your bike? (我可以借你的自行车吗？) You may go home now. (现在你可以回家了。)

[Example]—_______ I borrow your MP3? —Sure. Here you are. A. May B.Should C.Must D. Would

[Analysis] Here it indicates a request, meaning “can I do…?” The answer is: A

(2) Indicates conjecture, discussing possibility, meaning “may” or “perhaps”, usually used in affirmative sentences. For example: It may rain tomorrow. (明天可能会下雨。) She may be at home. (她可能在家呢.) “may not” translates to “may not”.

(3) The past tense of “may” is “might”, indicating a lower possibility than “may”. For example: He is away from school. He might be sick. (他离开学校了，可能是他生病了。)

He is away from school. He might be sick. (他离开学校了，可能是他生病了。)

(4) Indicates hope, prayer, or wish, often translated as “wish”. Generally used as “may + subject + verb”. For example: May you have a good time. (祝你过得愉快。) May you be happy! (祝你幸福！) May you succeed! (祝你成功！)

3. Usage of must:

(1) “Must” indicates subjective opinion, meaning “must” or “certainly”. For example: You must stay here until I come back. (在我回来之前你必须呆在这儿.) Must I finish my homework right now? (我必须现在交作业吗？) (Interrogative sentence led by “must”)

Affirmative answer: yes, you must.

Negative answer: No, you needn’t/ don’t have to.

(2) Its negative form “mustn’t” indicates “definitely not”, “absolutely not”, “prohibited”. For example: You mustn’t play with fire. (你不许玩火。) You mustn’t be late. (你一定不要迟到。)

(3) “Must” indicates a confident conjecture, used in affirmative sentences, indicating 100% certainty. For example: The light is on, so he must be at home now. (灯亮着，他现在肯定在家。)

(4) ① “Must” and “have to” both mean “must”, but the emphasis is different:

“Must” emphasizes the speaker’s subjective (personal) view.

“Have to” emphasizes the need from an objective (external) force, and can also be translated as “have to”.

I must go to school and learn some knowledge. (我必须会学校上课学一些知识。) (I need to return)

I have to go to school because the holiday is over. (假期结束了我不得不回学校上课了。)

② “Must” does not change with person or number, while “have to” has verb forms for singular third person:

has to and verb past tense: had to

Future tense: will have to

must not=mustn’t indicates prohibition…

When “must” is questioned, the affirmative answer uses “must”. The negative answer uses “needn’t” and “don’t have to”.

4. Usage of need:

(1) When “need” acts as a modal verb: indicates “need, must”, mainly used in negative sentences and interrogative sentences, its negative form is “needn’t”, meaning “no need”.

When asking with “need”, the affirmative answer is “must”, the negative answer is “needn’t” or “don’t have to”. For example: —Need I do my homework now? —Yes, you must. (是的。)—No. you needn’t / don’t have to. (不，你不必。)

(2) “Need” can also act as a main verb, in which case it changes with person, number, and tense.

If the subject is a person sb.:

sb. need(s) sth. (某人需要某物)

sb. need to do sth. (某人需要去做某事)

The singular third person of “need” is “needs”. The past tense is “needed”. The negative form uses “don’t/doesn’t/didn’t”.

For example: I need to pass the exam. (我需要通过这次考试。) He needs to learn English. (他需要学习英语。)

If the subject is a thing sth.:

Sth. need doing (某事需要被做) = need to be done

In this case, two points should be noted:

① The active form of the gerund “doing” has a passive meaning;

② The gerund can be changed to its infinitive passive form without changing the meaning of the sentence. For example: Your car needs washing. (你的车需要洗了。) = Your car needs to be washed. (你的车需要洗了。)

5. Usage of shall:

“Shall” indicates seeking the other person’s opinion (mostly used in first and third person), for example: Shall we go out for a walk? (我们出去散步好吗？)

In English, we can use various ways to make suggestions or seek the other person’s opinion.

“Shall” means “shall we… ?” or “is it okay…?” used in the first person, indicating the future, while “will” can be used for any person.

(1) Use “Let’s do…” to make suggestions. For example: Let’s go for a walk after supper.

(2) Use “What/How about…?” to make suggestions; “about” is followed by a noun or verb in the -ing form. For example: What about/How about a drink? What about/How about taking Tom with us?

(3) Use “Why not…?” to make suggestions, meaning “why not…”; “not” is followed by the base form of the verb. “Why not…?” is actually a simplified form of “Why don’t you/we…?” For example: Why not meet at the school gate at eight? Why don’t we stay here another day?

(4) Use “Would you like…?” to make suggestions, meaning “would you like…?” “Would you like” can be followed by a noun or infinitive. For example: Would you like a cup of tea? (你想要一杯茶吗？) Would you like to go and see her? (你想去看她吗？)

Therefore, if we say: “Shall we go swimming?” in English, it can be expressed in several ways:

Shall we go for a swim?

Let’s go for a swim, shall we?

What about/How about going swimming?

Why not go for a swim?

Would you like to go for a swim?

What do you think of going for a swim?

6. Usage of should:

“Should” means “should” and can indicate advice, suggestion, obligation, responsibility, etc. For example: We should protect ourselves. (我们应该保护自己。)

“Should not = shouldn’t” + base form of the verb

Usage of had better:

“Had better” means “better”, with no person change, followed by the base form of the verb; its negative form is: “had better not”. For example:

We had better go home now. (我们最好现在回家。)

You had better not go home now. (你最好现在不要回家。)

“Should” and “had better” can be interchangeable.

“Should not = shouldn’t” and “had better not” can also be interchangeable.

7. Usage of will:

“Will” indicates willingness, intention, or plan, and can be used for various persons. For example: I will help you if I’m free this afternoon. (今天下午如果我有空，我就会帮你。)

② It is the marker for the simple future tense., “will + base form of the verb”.

Note:

1. The form of “will” in the “there be” sentence pattern and its sentence transformation.

Since the structure of the “simple future tense” can be expressed using “will + base form of the verb”, the form of the simple future tense of the “there be” sentence pattern is “there will be”. (一定不能说 there will have)

For example: There are many students in our school. → There will be many students in our school. (我们学校有很多学生。) There will be a sports meeting next week. (下周一定会有一场运动会。) It must not be said: There will have a sports meeting next week.

2. The difference between “will” and “be going to do sth”:

① “Be going to” indicates intention, plan, or arrangement to do something, or a sign that something is about to happen;

“Will” indicates a future time that is farther away, for example: He is going to Beijing on National Day. (他国庆节要去北京。)

He will write a book someday. (他将来会写一本书。)

② “Be going to” indicates something that will definitely happen in the future based on subjective judgment, while “will” indicates something that will inevitably happen objectively in the future.

For example: I am going to be a teacher. (我打算成为一名老师。)

He will pass the exam because of hard work. (他会通过考试，因为他努力学习。)

③ In the main clause of conditional sentences, “be going to” is generally not used, while “will” is often used, for example: I will go to school if I feel better. (如果我感觉好点，我就会去学校。)

Point 2: Responses to interrogative sentences containing modal verbs:

1. For questions led by may, the following responses can be used: Yes, you may. Yes, of course. Yes, certainly. Sure.

No, you mustn’t. No, you can’t.

2. For questions led by must, the response is: Yes, …must. No,… needn’t/ don’t have to.

3. Could in interrogative sentences indicates a polite tone, and at this time, “could” does not carry the meaning of past tense. For example: Could you do me a favor? (你能帮我个忙吗？)—Could I use your pen?—Yes, you can. (可以。) (No need to answer with “could”).

4. Shall led interrogative sentences are used in the first person to seek the other person’s opinion or politely request. The following responses can be used:

Yes, please. All right. No, thank you.

5. Responses to would you… can include: Yes, I will. (No, I won’t.) Sure. (I’m sorry, I can’t.) All right/ OK/ With pleasure. Certainly. (No, thank you.) Yes, please.

[Example]—Would you give me a hand and pass my thanks to Lily? —________.

A. That’s right B. With pleasure C. It doesn’t matter D. No trouble

[Analysis] A means “That’s right”, B means “I would be happy to help”, C means “It doesn’t matter”, D means “No trouble”. Answer: B

6. Will you ………? can be answered using yes,…../no…… or I’d be glad to….

Point 3: The different negative meanings of modal verbs:

1. (1) can’t can be translated as “cannot”, for example: I can’t play basketball. (我不会打篮球。)

(2) When a sentence expresses conjecture, “can’t” conveys “impossible”, for example: He can’t be ill. He is playing chess with Tom. (他不可能病了，他正和Tom下棋呢。)

(3) “Can’t” can also be used to answer questions like “May I …?” For example: May I come in? (我可以进来吗？) No, you mustn’t. / can’t. (不，你不能。)

(4) “Can’t” can also be used in fixed expressions. For example: can’t help doing (禁不住，情不自禁) can’t wait to do sth (迫不及待) For example: She can’t help crying. (她不禁大哭起来。) The children can’t wait to open the box. (孩子们迫不及待地想打开盒子。)

2. May

Its negative form is “may not”, translated as “may not”, for example: He may not be at home. (他也许不在家。)

3. (1) Mustn’t means “prohibited” or “not allowed”. For example: He mustn’t leave his room. (他不许离开他的房间。) You mustn’t talk in class. (你们不可以在课上说话。)

(2) “Mustn’t” can also be used in negative responses to requests made using “may”. For example: —May I stand here? (我可以站在这里吗？) —No, you mustn’t (can’t). (不，不行。)

4. Needn’t

Means “no need”. For example: You needn’t meet him unless you’d like to. (你不需要见他，除非你愿意。)

5. Shouldn’t indicates “should not”. For example: You shouldn’t feel so unhappy over such little things. (对于这种小事，你不应该感到这么不高兴。)

Point 4: The usage of modal verbs to indicate conjecture:

1. “Modal verb + base form of the verb” indicates conjecture about the present.

1. Must indicates a strong conjecture, 100% certainty, generally used in affirmative sentences.

For example: He must be at home because the light is still on. (他肯定在家，因为灯还亮着。)

2. Should indicates a higher possibility of conjecture, less than must.

For example: It is already 10 o’clock now they should be there. (现在已经10点了，他们应该到了。)

3. Can generally used in negative sentences or interrogative sentences when indicating conjecture.

For example: Who is knocking at the door? Can it be the postman? (谁在敲门？可能是邮递员吗？)

Could indicates conjecture, with a weaker tone than “can”, leaving room for the speaker.

—Could it be an animal? (那可能是动物吗？)

—It could not be, because it is not moving. (那可能不是，因为它没有动。)

4. May indicates conjecture, used in affirmative sentences. Might can also indicate conjecture but indicates a lower possibility than “may”.

For example: The man may be your new teacher. (那个人可能是你的新老师。)

—Where is Mr. Li? (李先生在哪里？)

—He might be working in his office. (他可能在办公室工作。)

[Summary of Confusing Points of Modal Verbs]

Confusing Point 1: Can and be able to:

Both indicate ability but “can” has only the base form “can” and the past tense “could”; in other tenses, “be able to” must be used. Additionally, “be able to” often refers to achieving something after effort, time, and labor.

For example: Jim can’t speak English. (吉姆不会说英语。)

He could speak English at 5. (他五岁时就会说英语。) We’ll be able to see him next week. (下星期我们将会见到他。)

He has been able to drive. (他已经会开车了。)

I’m sure you’ll be able to finish it quickly. (我相信你能迅速地完成。)

We were able to reach the top of the mountain at noon. (我们能在中午到达山顶。)

Confusing Point 2: Can and may

Both “can” and “may” can be used to seek permission, meaning “can”, and are generally interchangeable.

For example: Can/ May I help you? (我能帮助你吗？)

2. The difference between “can” and “may” when indicating conjecture/possibility:

Can indicates refusal, while May does not ask.

1) Use “might”, “may”, “must” in affirmative sentences, not “can”; for example: She may be in the classroom. (她可能在教室里。)

2) In negative sentences, use “can’t” (impossible), not “may” or “must”.

3) In interrogative sentences, use “can” to indicate conjecture, not “might”, “may”, or “must”.

Where can they be now? (他们现在可能在哪儿？) That can’t be true. (那不可能是真的。)

Confusing Point 3: May be and maybe

Usage Difference	Common Position
May be	“May” as a modal verb, “be” as the base form of the verb	In the sentence, as the predicate
Maybe	Adverb, meaning “perhaps” or “maybe”, equivalent to “perhaps”	At the beginning of the sentence, as an adverbial

For example: He may be wrong, but I’m not sure. (也许他错了，但我也不确定。)

Confusing Point 4: Can’t and mustn’t

1. “Can’t” can be translated based on its basic usage:

(1) Cannot. For example: I can’t speak English. (我不会说英语。)

(2) Cannot. For example: We can’t do it now because it’s too dark. (天太黑了，我们现在干不了。)

(3) In negative sentences, it indicates conjecture, “impossible”, for example: The man can’t be our teacher because he is much younger than our teacher. (那个人不可能是咱们老师，他年轻得多。)

2. “Mustn’t” means “prohibited” or “not allowed”, used to express commands, indicating strong tone. For example: You mustn’t play football in the street. (你不可以在街上踢足球，太危险了。)

Confusing Point 5: Must and have to

1. “Must” emphasizes personal will and subjective necessity, while “have to” emphasizes objective necessity and can be used in present, past, and future tense.

For example: I know I must study hard. (我知道我必须努力学习。)

My brother was very ill, so I had to call the doctor in the mid-night. (我弟弟病得厉害，我只得半夜里把医生请来。)

I haven’t got any money with me, so I’ll have to borrow some from my friend. (我身上没带钱，只好向朋友借点了。)

He said they must work hard. (他说他们必须努力工作。)

2. “Have to” can be used in various tenses; however, “must” is only used in the present or future.

For example: The composition is due to hand in this morning, so I had to finish it last night. (作文今天早晨到期，因此我不得不昨天晚上完成。)

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