中学英语微课

Hello, everyone! Today we're going to learn about a very important part of English grammar： Imperatives and Modal Verbs. These are really useful in our daily communication, so let's start this interesting learning journey together~

This lesson covers: Imperatives.Modal Verbs: can , must , and have to.Key differences between must and have to. A summary to tie everything together.

Look at this. What are imperatives?

Imperatives are sentences used to express commands, requests, advice, warnings, or prohibitions. The subject of an imperative sentence is usually the second person, but we often don't say it out. Most imperative sentences begin with the base form of a verb, except for the "No" type. And there are four main types of imperative sentences: Do - type, Be - type, Let - type, and No - type. Let's learn more about each type in the following slides.

Let's start with the Do - type imperatives. In the affirmative form, we just use the base form of a real - action verb followed by other elements. For example, "Go away." It's a simple command. "Listen carefully." We use it when we want someone to pay attention. When it comes to the negative form, we add "Don't" in front of the base form of the verb. Like "Don't draw on the wall." It's a warning. "Don't run." This is also a common command.

Next is the Be - type. In the affirmative form, we use "Be" plus an adjective or a noun phrase. For instance, "Be nice." We use this to encourage someone to be kind. "Be a good boy." It's a request. In the negative form, we use "Don't be" plus an adjective or a noun phrase. Such as "Don't be nervous." We say this to comfort someone. "Don't be a bad person." It's a strong advice.

Now, the Let - type. In the affirmative form, we use "Let" plus an object and then the base form of a verb, like "Let's go home." It's a suggestion. "Let me try." Here, "me" is the object. For the negative form, we can say "Don't let" plus an object and the base form of a verb, or "Let" plus an object and "not" and the base form of a verb. For example, "Don't let him touch it." and "Let him not touch it." They both mean we don't want him to touch something.

The No - type is quite special. It's always in the negative form. We use "No" plus a noun or a gerund to express prohibition. For example, "No photos." When you see this sign, it means you can't take pictures. "No fishing." It tells you that fishing is not allowed there. "No swimming." It's a warning that swimming is prohibited in that place.

Now, let's move on to modal verbs. There are three important principles for modal verbs. First, modal verbs can't be used alone. They must be followed by the base form of a verb. Second, modal verbs don't change according to the person or the number of the subject, except for "have to". Third, to make a modal verb negative, we usually just add "not" after it, but for "have to", the negative form is "not have to".

Let's talk about the modal verb "can". One of its main uses is to express ability. For example, "He can swim." It means he has the ability to swim. "I can jump." It shows my ability to jump. "They can run." It tells us that they are able to run.

"Can" can also be used to express permission. For example, "You can play basketball at the weekend." It means you have permission to play basketball on the weekend. But sometimes, we use the negative form. For example, "We can't run in the hallways." It means running in the hallways is not allowed. "You can't litter." It's a rule that you are not permitted to litter. The negative form of "can" is "can not", and we usually abbreviate it as "can't".

Another important use of "can" is to make requests. For example, "Can you help me with my Chinese?" It's a polite way to ask for help. "Can we bring our phones to class?" When we want to know if it's allowed, we can ask like this. The answers are "Yes, subject + can." or "No, subject + can't." For example, "Can I open the door? Yes, you can." or "No, you can't."

Now, let's learn about the modal verb "must". "Must" means "必须". For example, "We must keep them in our lockers." It's a rule we need to follow. "You must read a book before you watch TV." It's a requirement. The negative form of "must" is "must not", and we often abbreviate it as "mustn't". For example, "mustn't litter." It means littering is prohibited.

Next is "have to", which also means "不得不，必须". For example, "We have to be quiet in the library." Because it's a library rule, we have no choice but to be quiet. "She has to do her homework first when she gets home." It shows an obligation. "We have to eat in the dining hall." It's something we need to do according to the rules.

"Have to" and "must" are quite similar in meaning sometimes. For example, "We have to / must follow the rules." In this case, both can be used to express the need to follow the rules. But they also have some differences. Let's look at them carefully.

Look at these examples. "We must hurry. I don't want to miss the beginning of the show." Here, "must" shows the speaker's subjective opinion. The speaker wants to hurry because of their own feeling. "We have to hurry. The train is leaving in five minutes." Here, "have to" emphasizes an objective need. We have to hurry because of the situation of the train. So, "must" usually shows the speaker's subjective view with a stronger tone, while "have to" emphasizes the objective need.

Let's look at the negative forms. "You mustn't talk to your mother like that." "mustn't" means "不准、禁止". It's a strong prohibition. But "You don't have to come if you don't want to." "don't have to" means "不必". Their negative meanings are quite different.

Look at the forms with different subjects. "I/We/You/They/He must do something about it." "must" doesn't change with different subjects. But "I have to finish my work today. She has to work late today. They have to get to the station before 5 o'clock." "have to" changes according to the person and number of the subject. So, "must" has no change in person and number, while "have to" does.

Let's summarize what we've learned about imperatives. Imperatives are sentences used for commands, requests, advice, warnings, and prohibitions. They usually start with the base form of a verb (except for the "No" type) because the subject is the second person. And we have four types: Do - type, Be - type, Let - type, and No - type.

You can refer to the table on the slide to review.

Finally, let's summarize modal verbs. Remember the three principles of modal verbs.

And we learned about "can", which can express ability, permission, and requests. Its negative form is "can't". For "must" and "have to", although they both mean "必须", "must" emphasizes the subjective view, and "have to" emphasizes the objective need. Their negative forms also have different meanings, and "have to" has changes in person and number while "must" doesn't.That's all for today's class. I hope you've learned a lot. If you have any questions, feel free to ask me after class.