Lesson Transcript

Hi, everybody! My name is Alisha.
In this lesson, I'm going to talk about the differences between "must," "have to," and "should." I'm also going to talk quickly about the negative forms. I'm going to focus on comparing the very similar meanings of these words. So, let's get started!
First, let's talk about "must."
In the negative, we say "must not," so "must" or "must not." In British English, you may hear "mustn't," but we don't really use this in American English. We usually use "must not" when we want to use this pattern.
So, we use "must" and "must not" first for official rules. Official rules means, for example, rules at a company or rules at a school, rules at the airport, police, so law-related rules, like things that are related to your society. So official rules, we use "must" and "must not" to explain these rules.
For example…
"Passengers must show passports at immigration."
This shows it's an official rule. All passengers "must show," they have a responsibility, it's the rule. "Must" expresses this. It's a formal rule-like statement.
"Must not" then…
"Visitors must not wear shoes inside."
So that means, visitors must take their shoes off before coming inside. So "must not wear shoes inside" means not allowed. It is prohibited. You may not. It's not allowed.
So, "may not" means it's like less formal than "must not." "Must not" is much stronger. I'm not going to cover "may" in this one. So, "must not" is more formal. It sounds more rule-like, official rule-like.
The second use of "must" and "must not" is for strong personal advice.
Strong is the key here. I'm going to talk more about personal advice later in this lesson, but when you want to express strong personal advice, you can use must or must not. For example, like visiting a doctor's office or maybe some other kind of health-related issue or something that's very important to someone's life, you can use "must" and "must not" to express advice in those situations.
For example…
"You must stop smoking."
So, this might be advice, strong personal advice, for a very heavy smoker, someone who smokes a lot.
"You must stop smoking or you'll die."
"You must stop smoking or you're going to get much more sick," for example.
Another one...
"You must not forget to take this medicine."
So that means, you have a responsibility it's very important to take this medicine.
"You must not forget to take this medicine."
So we use this for strong personal advice, so "strong" is an important key word here. We don't use "must" for like, everyday general advice. I will talk about that later.
So official rules, strong personal advice, this is how we use "must" and "must not."
Let's continue to the second point for this lesson which is "have to," and the negative "don't have to." For different subjects, "doesn't have to" in the negative and in the positive, "has to." The same rules will apply to "need to" as well, need to. We also have "got to" in British English. So let's look at how we use these.
We use "have to" and the negative "don't have to" to talk about responsibilities.
So this can mean school responsibilities, work responsibilities, like relationship responsibilities, family responsibilities, the things that we have some kind of obligation to do. So in many cases, we don't want to do these things, but there's some need, there's some responsibility.
For example…
"I have to go to work."
"Have to" shows it's a responsibility. "I have to go to work."
"She has to leave early."
She has a responsibility to leave early, "she has to."
So as I said, when "she" or "he" or "it" is the subject, we conjugate the verb. We change the verb from "have" to "has." "She has to leave early."
These show a responsibility of some kind.
So many learners ask like, can I use "must" here?
"I must go to work."
"She must leave early."
It's not grammatically incorrect to say "must," "I must go to work," but because we use "must" for official rules and for like strong personal advice, it sounds kind of strange to use "must" here. Like, "I have to go to work," that's an everyday regular responsibility. When we make, like a sentence, like "I must go to work," it sounds like there's a very, like strong reason or there's a very official reason, "I must go." So you might hear that in movies like in epic, big scale, like fantasy stories. There's someone fighting a war, for example, or there's someone with a really big responsibility. They might say, "I must go." In those cases and when they're using like an old style of English, fine, but in everyday English, using "I must" before someone, like your responsibilities, sounds pretty strange, so I don't recommend it in most cases.
If you want to sound funny, you can say something like, "I must go to work." But in most cases, I would not recommend it. "I have to go to work" sounds much more natural, or "She must go..." or "She must leave early…," it sounds way too formal, so please use "has to" or " have to" to talk about your everyday responsibilities.
Now, let's look at negatives.
So again, "don't have to" is like the "I subject version."
"I don't have to..."
"We don't have to..."
"They don't have to."
If your subject is "he," "she," or "it," it becomes "doesn't have to."
"He doesn't have to..."
"She doesn't have to..."
So examples…
"He doesn't have to come."
This means he has no responsibility to come. It's okay. He doesn't have to come, no responsibility. He can, but he doesn't have to. That's what this communicates.
"He doesn't have to come."
Same thing here…
"We don't have to leave yet."
So "yet" shows it's okay now.
"We don't have to leave yet."
Maybe later.
"We don't have to leave yet."
Again, we can, but we don't have to. There's no responsibility there.
So an important point about the negative with "have to" or "need to" is that when you make a negative with this pattern, make sure you're talking about a common or a regular responsibility. We use these patterns, we use this "have to," this negative "have-to pattern" for things that we can reasonably be expected to have a responsibility to do.
So an example I have heard from students, from learners, is something like this…
"I don't have to drink alcohol at work."
So for grammar, this sentence is correct. The sentence is grammatically perfect. There's no communication problem. It's a great sentence, but this sounds strange because for most people, drinking alcohol at work is not a regular responsibility, I mean unless, unless you're like a bartender or you're someone who works with alcohol like a wine sommelier, whatever. But for most people, in this example, drinking alcohol at work is not a regular responsibility, so it sounds a little strange to say, "I don't have to drink alcohol at work."
We typically, we often regularly use "have to" in the negative, "I don't have to," to talk about our everyday responsibilities. So like, "I don't have to get up early on the weekends" means I have no responsibility to do that on the weekends. Or if you have a holiday, "I don't have to go to work today." That's a much more common way of using "don't have to," so please keep this point in mind. Make sure you're expressing a regular, like a reasonable expectation when you use the negative form here.
Okay, so with that in mind, let's continue to the last point for this lesson.
The last point is about "should."
In the negative, it's "should not" and we reduce "should not" to "shouldn't." "Should," "should not" and "shouldn't." We use "should" and "should not" for general advice, general advice. This means everyday, just regular life advice.
So, compare this to "must" and "must not" which we use for very strong personal advice. In most cases in everyday life, we use "should" to talk about general advice; a suggestion, a recommendation, we use "should" to talk about that. We do not use "must" to talk about that, unless for some reason, it's very, very strong.
"You should go home."
Maybe, you look sick.
"You should go home."
"He should take a day off."
Maybe, he looks stressed.
So using "must" in these cases would sound strange because these are kind of everyday small suggestions, like "You must go home," that sounds very serious. Or, "He must take a day off." Again, sounds very serious. Why? Did something happen? So, use "should" in these cases.
Also, using "have to" in these cases kind of sounds a little strange too. If I use "have to" here, "You have to go home," like why? Do I have a responsibility to go home? It's kind of strange. Same thing here, "He has to take a day off." Why? Like maybe there's some company rule, he has to take a day off, I don't know. But be careful, make sure if you're giving just advice, your opinion, just use "should."
Of course, there are some cases where you can use "have to" in place of "should" to make a stronger recommendation. This is useful when you're giving like a restaurant recommendation and it sounds like this…
"You have to try this restaurant."
So that sounds more, like excited than "you should."
"You should try this restaurant."
"You have to try this restaurant."
"Have to" sounds stronger because it's like you're saying, you have a responsibility to try this restaurant.
"You have to try this restaurant"
"You have to try this recipe."
It sounds a little stronger than "you should." So you can use it in that way. But if you're giving advice, like based on something you can see or if you're trying to give someone like career advice, maybe, be careful with your use of "should" and "have to." So, "have to" shows like you're putting responsibility on that person. So "should" is more like general advice.
Okay, let's look then at using "shouldn't."
So as I said, "should not" reduces to "shouldn't."
"We shouldn't talk so loudly."
So in this case, "we shouldn't," that's like advice for our group. Maybe, we're talking very loudly, and one person says, "Oh no, we shouldn't talk so loudly." So that's giving advice to the group. "We should talk more quietly." So, "We shouldn't talk so loudly."
Another one,
"She shouldn't worry so much."
So it's general advice, "Don't worry so much" is another way to say that.
"She shouldn't worry so much."
So again, using something like "must not" sounds way too serious here. Like, "We must not talk so loudly." It's for strong personal advice, so using "must" here sounds very strange. Same thing here, "She must not worry so much." Again, very strange because this is a very strong sounding expression. "She must not worry so much."
Similarly, using "have to" here, "We don't have to talk so loudly." That expresses lack of responsibility. We don't have to talk so loudly, but we can. It's kind of the idea there, so this doesn't sound natural. Same here, "She doesn't have to worry so much." This could be used perhaps, "She doesn't have to worry so much," like you could say in, for example, a work situation; you have a colleague, a co-worker, and she worries a lot, and you want to express to your manager or to your team member, "She doesn't have to worry so much. I can do it." Like in that case, maybe it's natural, but if you're giving general advice, "shouldn't" sounds much better.
So keep this in mind, "should" and "should not" for your general everyday advice, for recommendations. "Have to" and "don't have to" for your responsibilities. "Must" and "must not" for official rules and for very strong personal advice.
So, I hope that this introduction to these three expressions helps you understand the differences and the different feelings and situations in which we use these. So, if you have any questions or comments or if you want to practice making some sentences with these, please feel free to do so in the comment section of this video. Thanks very much for watching this lesson and I will see you again soon. Bye-bye!