Another two easily confused words this week. Fortunately, the difference between these two is fairly straightforward though the explanations I found online are a little bit confusing. I’ll do my best to describe the difference simply by giving examples of the 4 ways in which the two words are used: possibility, ability, making requests and offers, and asking for or giving permission.
“A cut can get infected if you don’t clean it”.
Can is used to show that something is very likely or certain to happen in the future.
“That cut could get infected if you don’t clean it”.
Could is used to show that something might happen in the future but there is a chance that it won’t.
Remember that can’t is used to show that something is prohibited or impossible:
“You can’t park here, it’s not allowed”.
“I can’t predict the future.”
“I can play the piano”.
Can is used to show the speaker is able to do an activity now.
“I could play the piano when I was younger”.
Could is used to show the speaker had the ability to do an activity in the past but (probably) cannot do that activity now.
“I can’t play the piano”.
“I cannot play the piano today! Hopefully I’ll do better tomorrow”.
Using can’t is easy: it shows that the speaker is unable to do an activity now. Cannot is often used to accentuate the idea (make the idea stronger), to express a feeling of frustration at being unable to do something the speaker can usually do.
Couldn’t is most commonly used to express the inability to do something in the past but the ability to do that action now:
“I couldn’t play the piano when I was younger, but now I can”.
3. Making requests and offers
“Can you pass the salt, please?”
“Could you pass the salt, please?”
The only difference between the two words here is that “could” is more polite than “can”. Think about how your language changes between when making requests of friends and family, and when you are talking to strangers or at work.
“I can send you the recipe, if you like”.
“I could send you the recipe, if you like”.
There’s no real difference between these two offers.
4. Asking for or giving permission
“Can I be excused from the table, please?”
“Could I be excused from the table, please?”
Like making requests, the only difference between the two words is that “could” is more polite than “can”. If you want to be very polite, use “may” instead.