Avoid an embarrassing grammar mistake by learning when to use “can” vs. “could” in different situations. While both “can” and “could” are forms of the same verb, they actually mean different things depending on the context. Keep these guidelines and examples in mind.
Can vs. Could Usage for Different Situations
When to Use “Can”
“Can” for Ability or Possibility
“Can” usually shows something may happen or is able to happen, as you can see by these examples:
We can find a prom dress to fit you.
The weather can be rainy in that part of the country.
I can speak four languages.
“Can” for Requests
You can also use “can” to make a request, as these examples show:
Can you help me finish this?
Can you open your math books to page 50?
Can you call me back in an hour?
Colloquial Use of “Can” for Permission
You can also use “can” colloquially for permission, even though it’s correct to use the verb “may.” “Can” sounds less formal, particularly in speech. In writing or in more formal speaking situations, it’s better to use “may.”
Can I go get a drink of water?
My mom says I can go over to Jenny’s house.
Can I ask you something?
When to Use “Could”
Once you understand the basic “can” grammar rules, you’re part way there. The confusion comes in when you think about when to use “could.”
“Could” for Past Ability or Possibility
In many situations, “could” is the past tense of “can.” It indicates something that was possible in the past.
We could have used that money to buy lunch.
I could ride a bike by the time I was five.
He could be really mean sometimes.
“Could” for Requests
Like “can,” “could” also works for requests. Here’s how to use it:
Could you show me how to address this letter?
Could you please be quiet?
Could you hold this for a minute?
Informal Use of “Could” for Permission
Like “can,” you can also use “could” to indicate permission. While “may” or “might” would be technically correct, “could” can be a slightly more formal version of “can.” It can also indicate the past tense of “can” in this situation.
He said I could have a balloon.
Could I use your restroom?
Could I please get your signature on this petition?
“Could” for Conditional Future Scenarios
A less common way to use “could” involves future scenarios that might happen. This is called a conditional sentence, and you use the past tense when you write it. These usually start with “if,” but sometimes, they also involve “I wish.” Here are some examples with “could” used in this way:
If he bothered to ask me to the dance, I could give him my answer.
I wish I could have known my grandfather.
If we went to the store, we could buy everything we need for a special dinner.
How Likely Is It to Happen?
When you’re talking about the future, use of “can” and “could” tells the reader or listener how likely something is to happen. In many cases, “can” expresses that something is certain, while “could” indicates it may or may not happen.
For instance, imagine you are saving money to buy a new car. When you talk about your plans, “can” sounds much more certain than “could.”
I can buy a new car in January because I will have enough money by then.
I could buy a new car in January because I will have enough money by then.
Easy to Use Correctly
Although they may seem complicated at first, “can” and “could” are easy to use correctly once you know the rules. Understanding this type of basic English grammar helps improve your writing, and it gives you the confidence to express yourself.