Lesson Transcript

Hi, everybody! My name is Alisha.
In this lesson, I'm going to talk about the differences between "can" and "could."
This lesson is going to include a lot of information and some example sentences. If you want to know more about any of these points, try searching our YouTube channel for a lesson with some more details.
Okay, let's get started with the first point, number one up here.
The first way to use "can" and "could" that I want to talk about is "to express abilities."
So, an "ability," that refers to something we are able to do or not able to do. When we want to talk about a present ability, something we can do now, I just used "can" to express that, something we have the ability to do now, we use "can" + [present tense verb]. This expresses a present ability, something we can do now. It's possible for us to do that now.
To make the negative form, we use "cannot" or "can't." I can't do something.
When we want to talk about a past ability, for example, something in our childhood or something when we were in school, we use "could" + [a present tense verb], again. So this verb, in past and present form, uses a present tense in this position, this verb here. We always use a present tense verb in this position. This expresses a past ability. We know this because we're using "could" in this pattern.
Let's take a look at a couple of examples of this.
First, a pair of present tense statements.
The first one here is:
"I can speak English."
So, a very basic pattern, hopefully, many of you can use. Here, we see "can" plus "speak" in this case. "Speak" is a present tense verb and then we have the language here. So a reminder, we use "speak" when we're talking about our language ability. It's not, "I can't talk" or "I can say" but "I can speak" English.
Of course, we could change this to a negative, "I can't speak French" for example. We can use the same pattern, just replacing "can" with the negative "can't."
Let's look at a different one now.
"She can't swim."
So here, my subject has changed, yes, to "she." There's no change here to reflect the subject and "swim," my verb, following "can't" remains in the present tense.
So these are very basic examples of how to express our abilities with "can" and "can't" in the present.
So, let's compare this then to using "could" to make past tense expressions. So, as I said, "could" will change from "can" to "could" but the verb does not change.
Let's see how we use this.
"He could speak Spanish when he was a kid."
This is a past tense ability statement and something you'll notice is very common in these past-ability statements is a point in time or like a time period "when." So, "He could speak Spanish (when), when he was a kid." So you'll notice, this is also in past tense, not, "when he is a kid," "when he was a kid." At that point in time in the past, it's finished now. So, we'll often include a time period or a point in time in the past to help us understand this ability.
One more example here. This is a negative example.
"We couldn't watch the movie. It was too violent."
So here, this is a past tense negative. "Couldn't" is the reduced form of "could" and "not."
"We could not watch the movie."
So we could say, yes, this is kind of like a possibility statement which I'll talk about a little bit later, but we can also use this kind of expression to explain, it was not possible for us to watch the movie, like I didn't have the ability to watch that movie. We might use an expression like this. So the reason here, instead of a point in time which we probably understand from the situation, like we couldn't watch the movie last night or we couldn't watch the movie last weekend, instead of a point in time, I included a reason. So why couldn't I watch the movie or why couldn't we watch the movie? "It was too violent." So "it" is the movie. The movie itself, this was past tense, a past situation, "violent," violent so this means there's like, maybe like action, people attacking other people, hurting other people, maybe very graphic scenes, extreme or intense images, it's too violent. So we can use "couldn't" to talk about these kinds of things too. I'll explain a little bit more when I talk about Point No. 3, in this lesson.
So, this is how we use "can" and "could" for present and past tense abilities.
All right. Let's continue on to Point No. 2 for this lesson. Point 2 is using "can" and "could" for requests and for offers. So this is actually a bit simpler than this point, I think. The difference here when you're making requests and offers with "can" and "could" is just that "can" sounds more casual, it sounds a little bit more friendly. "Could" sounds a bit more polite. So, both of these are okay to use in most situations. If you want to sound a little bit more formal, a little bit more polite, you can use "could." In most everyday situations, we use "can." So we begin our request or our offer, usually, with can and we make a question with it. There are a couple of other variations too. I'll show you a couple of examples. So, let's look at using "can" first.
So, let's begin our sentence, our question with "can" here.
"Can you help me with my homework?"
This is a request. "Please help me," in other words. So instead of, "Please help me with my homework" which sounds, like we're desperate maybe, "please help me," using "can you" is kind of like asking, "Do you have the ability to help me with my homework?" "Is it possible" "Would it be okay?" So it's a bit softer than using "please." So "Please help me." It's okay. There's not a communication problem, but, "Can you help me with my homework?" sounds a bit nicer, a little bit more friendly.
Now, let's look at using "can" to make an offer.
"I can buy you a coffee, if you like."
So, "if you like" is like if you want one, if it's okay, do you want one, if you like. A nice offer expression.
"I can buy you a coffee."
So here, in the offer pattern, "can" comes before the verb. So again, we can think of this a little bit like an ability. So, it's like the speaker is saying, "Right now, I have the ability to buy you a coffee. Would you like a coffee?" But that doesn't sound natural. It's like saying, "Right now, this is possible. I can buy you one, so is that okay?" "I can buy you a coffee, if you like." So this is a nice, friendly way to make an offer.
Let's compare this then to using "could" in similar patterns.
So as I said, "could" is going to sound a little bit more formal, a little more polite.
First example is a request.
"Could you please send me the files?"
So, I've added "please" here to show, again, it's a little more formal. And in this case, perhaps, it's a business situation. Maybe it's a business situation, "send me the files." So, this is a work request, perhaps. Maybe that's why the speaker is using "could" and "please."
You'll also notice that when I'm using "could" or "can" to create a request question, I'm following the word "can" or "could" with the person I want to help me. So in this case, I'm using "you" for both of my sentences, but you might hear some sentences where the speaker asks for someone else to do something, so this person is not in the conversation, I'm talking to someone else. I would like, ask this person, please ask that person to do something like, "Can he join the meeting later?" for example. That's something that you might hear too. For this request and for probably a lot of requests though, we use "you" after can or could, but you may hear "he" or "she" or they used in these patterns too.
Okay, let's finish this part with an offer using "could."
"If it's helpful, we could teach your staff about the new software."
"If it's helpful," so again, it's a softening expression, kind of like if you like, but this sounds a little more formal, if it's helpful, if you like, we could teach your staff about the new software. So this is an offer. We are offering to teach your staff about the new software. We use "could" to do that. We could do this, like again, we have this ability, yes, but in this case, "could" is not referring to a past-tense situation. We're using "could" to make a polite offer, "We could teach your staff." So, this is one example of how to do it. Okay. So, this is how we use "can" and "could" to make requests and to make offers.
Let's continue then, I want to move back to this side of the board, to Point 3 for this lesson. So, I talked a little bit about this in Point No. 1, but we also used "could" to talk about present and past possibility. So first, let's look at a couple of sample patterns. This is probably, I think, these two, the most common patterns you might hear to use "could" and "could not."
So, first, an explanation. In many of these possibility statements, we use "could" plus the verb "be" plus often, some kind of, like adjective phrase. When we make the negative form, we use "could not" plus the verb "be" plus our adjective phrase. So, when we make a past tense possibility statement, we follow a similar pattern, but we use "have" been instead of "be." So, this pattern is our present tense possibility statement, present situation, "have been," this "could have been" pattern refers to a past possibility.
So, let's take a look at some example sentences that use these patterns.
First:
"Hmmโ€ฆ the meeting starts at 2:00, but nobody is here. I could be in the wrong place."
So here is my "could be." So, I included this part to show the situation. Situation and context are quite important for these kinds of statements. So in this case, the speaker is waiting for a meeting that starts at 2:00 and the speaker is thinking to himself or herself, "Hmmโ€ฆ the meeting starts at 2:00, but nobody is here, so I could be in the wrong place." Another way to say that is, "It's possible I am in the wrong place." "Wrong" means incorrect. I'm in an incorrect place. The meeting is somewhere else.
So, "could be" expresses this possibility. There's a possibility I'm in the wrong place. You might also hear "might" used here instead of "could." "I might be in the wrong place." So, the difference between "might" and "could" is very small in this situation. "I could be in the wrong place" is very neutral. It's not like positive or negative. There's not a high chance or low chance, just it's possible. If I said, "I might be in the wrong place," it sounds like there's a higher chance, like maybe a 50% or 60%, it's not a rule, but there's a higher chance I'm in the wrong place, like "Hmmโ€ฆ I might be in the wrong place" sounds a little bit more certain than, "I could be in the wrong place." So it's just a level of certainty there. So, "I could be in the wrong place."
Let's look at another example. This one is a past situation, a past situation. It's a conversation.
Person A says, "Hey! Was that Michael?"
So you're on the street, "Was that Michael over there, in that coffee shop?" for example.
B says, "No, that couldn't have been Michael. He's out of town."
Out of town, so "out of town" means away from the city. So here, I'm using "couldn't have been Michael," so that means that guy over there, you pointed to, that couldn't have been Michael. "Could not have been," this means it's impossible, that was Michael. There's no chance. Absolutely, no chance that was Michael. I know because he's out of town, he's out of town, he's not here.
So, "couldn't have been" means impossible. That couldn't have been Michael, he's out of town. So we use these two patterns to express possibility and yes, please, keep in mind that this negative I've used here, "couldn't have been," means not possible, not possible. So "couldn't be" as well, the negative in the present form is also reflective of an impossible situation. So here, I used the positive "could be" meaning it's just possible, but when you use the negative form, it means something is impossible. So, for example, let's imagine the speaker in this situation came to the correct place. So, the speaker looks at his or her watch, and says, "Hmm, the meeting starts at 2:00 o'clock and everybody is here, I couldn't be in the wrong place." It's impossible I'm in the wrong place because everybody is here, I know I'm in the correct place, so I couldn't be in the wrong place, I'm in the correct room. So impossibility is reflected with the use of the negative form. With the positive form, it's just a simple possibility, very neutral.
Final point here, we make questions with these same kind of pattern. So we do this often when we're thinking, like thinking to ourselves, so I'm alone and I'm thinking to myself about something or when I need to confirm something with someone else.
So an example:
Could this be the correct building?
So, "Could this be the correct building?" I would use this if I'm checking with my phone, checking the GPS on my phone, searching for a place, "I have a meeting (something)," I'm looking around and I think this building is correct. I think to myself, "Hmm, could this be the correct building?" So that's a sentence or a question a native speaker might say.
I feel, in most situations though, we just say, "Is this the correct building" We just say it with "is." "Could this" sounds more like, "Is it possible this is the correct building?" So it might sound a little bit more formal. I feel like, in everyday speech, more commonly, we say, "Is this the correct building?" but you might sometimes hear "could" used in this kind of pattern.
Let's look at one more example:
"Could I have made the wrong decision?"
So again, the speaker is thinking about something in the past or maybe they're speaking to a friend. "Could I have made," we know this is a past expression because of this grammar right here, "could I have made," "have made" shows us that this is something the speaker chose to do in the past. So, "Could I have made the wrong decision?" It could be, the speaker is thinking out loud to himself or herself. Is it possible, I made the wrong decision? Or, the speaker could be asking someone else, "Could I have made the wrong decision?" and they're expecting some kind of opinion.
So, we're using these patterns to talk about possibility. So, you might hear some questions that use "could" in this way, but keep in mind, these are a little bit different from these offer-type questions we talked about.
Okay. Let's move along then to Point No. 4 for this lesson. Point No. 4 is about unreal situations, unreal situations. So, when we use "could" with unreal situations, there are quite a few patterns that we can use, but I wanted to introduce just a couple of very, kind of simple ways that we use this. So, I've made just this very simple pair of [if clause] and [main clause] and I've got here [main clause with could]. So, a point to be careful of is when you're making your unreal statement and you're using this "if (something, something)" "main clause (something, something)" pattern, make sure your "could" is in your main clause. We do not use "could" in the "if clause" so no "could" goes here. Your modal verbs in general, don't put them in the if clause. Put them in the main clause, so that means like "will, won't, may, might," all those words, put them in your "main clause," "could" as well.
So, there are a few different patterns that we use with unreal situations. I want to talk about these two. They have a little bit of challenging grammar, so let's take a look.
First one:
"If I won the lottery, I could buy a house."
Here's my "if clause," "If I won the lottery, I could buy a house."
So here is "could." So "could" is used, yes, to talk about this unreal situation, so we know it's not real because of this "if" right here. So that means, I have not won the lottery, by the way, "lottery" is a game, so we can win a large money prize by chance, so we buy a card or a ticket and maybe we get a large prize for that. It's a game, kind of gambling. Anyway, "If I won the lottery," maybe, I have not won the lottery, but if I did, I could buy a house. So this "could" is reflective of this possibility point or kind of you can think of it as this ability point too a little bit, but it means, I would be able to. So I would have lots of money, so it would be possible to buy a house. So we use "could" to reflect that. If I won the lottery, I could buy a house, possibility here, so we do not use "can" in this case. We use "could" because it's an unreal situation. We don't use this "can" to talk about this unreal situation. Please use "could" here.
Let's upgrade a little bit, more challenging grammar here, "if clause" again.
"If we had finished work earlier today," if clause.
"If we had finished work earlier today, we could have gone to the movie theater."
"We could have gone to the movie theater."
So, this is a very challenging sentence to understand. Let's take a look. "If we had finished work earlier," earlier today, earlier than we did, so we finish work at 8:00 PM, but "if we had finished," so this is referring to a past action. It's complete, if we finished work or if we had finished work at 5:00 PM, for example, earlier than we finished, we actually finish at 8:00, but if we had finished earlier, maybe 5:00, we could have gone to the movie theater. So, "could have gone," this use of "could" refers to an activity in the past, a possible past activity that would have been possible, if this part were true. So again, to recap, we finished work at 8:00. We could not go to the movie theater in this situation, but if we finished work earlier, if we had finished work earlier, for example, 5:00 PM, in that situation which is not real, did not happen, we could have gone to the movie theater. It would have been possible.
So we use these kinds of sentences to talk about all this stuff in the past that did not happen, but we just want to dream about it. So this is an example of how we use "could." And again, we use "could" here, not "can." We make a past tense example or a past tense pattern, rather, by using "have" plus "the past participle form of the verb." So again, a challenging grammar point, but this is one we use a lot to dream about a past situation.
Okay, let's finish this lesson with Point No. 5, kind of a small point.
So, I want to go back to Point 2 here. We talked about using "can" and "could" to make requests and offers. Another thing you might hear is using "can't" and "couldn't" to make suggestions. So, you'll notice all of these use the negative form. So, the difference here is that when you use the positive as we talked about in Point 2, positive form sounds a bit more like a request. It's like you want something. When you use the negative though, it's like you're giving something, you're giving a suggestion, so using the "can" is a little more like you're pulling, maybe information or you're pulling something. Using "can't" is like you're giving a suggestion or you're giving advice.
So, we use "can't" or "couldn't" in the same way that we use "can" and "could" to sound a bit more polite. And, we often pair this, we often use this together with "just." "Just" is like a modifier. It changes the feeling to sound like simpler or a little more gentle, like just a simple suggestion, just a small suggestion. So "can't you," for example, "you" is very common here as I talked about in these patterns, but we can use "he, she, they, we," and so on. Plus for present tense situations, for present tense sentences, suggestions, we use a present tense verb here.
For "couldn't," we can talk about, again, present tense situations or we can imagine, as we did here, we can imagine a past-tense situation and you want to give advice, you want to give a suggestion about that past situation, you can do that with "couldn't" plus past participle verb form as we did here.
So, some examples of these.
First:
"Can't you just leave earlier?"
So someone who's always late, for example, "Can't you just leave earlier?" You could remove "just" that's okay, "Can't you leave earlier?" but "just" softens it. It's like this is a small suggestion, "Can't you just leave earlier?"
Another one:
"Couldn't you just call to confirm?"
It's a small suggestion, so it sounds a little more polite because we're using "couldn't" here.
Finally:
"Couldn't you have created a bigger budget for the project?"
So, this is another past tense situation, so we're dreaming here again. So, "Couldn't you have created" shows us this was a past thing that someone did, the listener did, so the speaker created, or sorry, the listener created a budget for the project. The speaker is saying, "Couldn't you have created a bigger budget for the project?" So, this is giving a suggestion or rather, the speaker's opinion about a choice or a decision the listener made in the past." So we use these negative forms to give suggestions, to give advice, to give opinions, not so much requests or offers.
Okay. So, that's a lot of information, a lot of different ways to use "can" and "could" and also, there are some patterns, there are many patterns that I did not talk about in this lesson, so you can try to, I think, use these five points, maybe, to understand a little better the different uses of "can" and "could" as you listen and as you read as well.
So I hope that this is helpful for you. Again, if you want to know more about any of these points, you can try searching our YouTube channel to see if there's another whiteboard video specifically about one of these points, so please take a look at that. Okay.
Thanks very much for watching this lesson and I will see you again soon. Bye-bye!

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Hello Ernesto Martinez,


Thank you so much for your kind message! ๐Ÿ˜‡โค๏ธ๏ธ

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Ernesto Martinez
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Excellent explanation

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Hello Alejandra Barahona,


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Alejandra Barahona
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A lot of information but super well explained!

Thank you so much, this is very helpful.