Difference between Could and Can

Updated on March 22, 2017

The sentences “Could you help me?” and, “Can you help me?” both make sense and are grammatically correct, so it’s no wonder why some English learners think the words “could” and “can” are interchangeable. Although the two words have similar meanings, they actually have different functions and are not always interchangeable. In this article, we will explore the difference between “could” and “can.”

Descriptions

Could

The word could is the past tense of “can.” It is used:

  • To talk about an ability or a skill a person had in the past; for example: When my mom was younger, she could finish a knitted scarf in an hour.
  • To describe something that was generally possible in the past or something that you think is likely to be true; for example: Many years ago, you could buy a pair of pants for two dollars.
  • To make a polite suggestion or request, or to ask a question politely; for example: Could you please tell me where the bus station is?
  • To talk about something that is possible in the future but you are unsure of (hypothetical); for example: If you don’t fill out that form now, your application could be declined.
  • To describe something that people were allowed or permitted to do in the past in general; for example: In 1975, the employees of ABC Corporation could wear shorts and slippers to work.

Aside from being used similarly to “can,” “could” also has other uses:

  • To refer to something that you wish you have or can do but that is not possible; for example: If only I could buy my mom a new car!
  • To talk about something that was possible but did not occur (paired with “have”); for example: Sasha could have won the pageant if she had not backed out.
  • To express a strong emotion (i.e. disappointment) when you expected something but it did not happen; for example: I don’t want to hear your reasons! You could have helped me if you wanted to!
  • To emphasize a feeling by exaggerating it to the point that it becomes unrealistic; for example: I’m so exhausted I could sleep for 3 days straight!
  • To describe a conditional situation wherein something has to happen first for something else to occur; for example: You could lose weight if you stop drinking bottles of soda every day.

can

On the other hand, the word can is used when talking about something that is current. It is used:

  • To talk about an ability, skill, natural characteristic, or something learned; for example: My father can speak English, German, Italian, and Spanish.
  • To ask for permission to do or say something; for example: Can I borrow these Julie Newman books?
  • To give permission or make a suggestion; for example: You can go home at 3:30 PM.
  • To describe a possibility or something that might happen in the future; for example: It can get really hot during the summer.
  • To describe an impossibility (paired with “not”); for example: This so-called news can’t be true!
  • To talk about things that you are allowed or not allowed to do in general (present); for example: The senior students of St. Anne’s Catholic School can have a two-hour lunch on Fridays.

Could vs Can

What, then, is the difference between “could” and “can”?

“Could” has the same functions as the word “can” except that “could” refers to things that happened in the past and “can” refers to things that are current. This means that both “could” and “can” can be used to express an ability, possibility, suggestion, or things that are permitted in general.

Additionally, “could” is also used to express a wish or a strong emotion, talk about a possible event that did not occur, emphasize an exaggerated feeling which makes a situation unrealistic, or describe a conditional statement. In these cases, “can” should not be used to replace “could.”

Going back to our example in the beginning of this article, “Could you help me?” and “Can you help me?” are indeed both grammatically correct since in this case, “could” and “can” are interchangeable (both are used to express a request or ask a question). However, using “could” gives the sentence a more formal or polite tone than using “can.”

Comparison Chart

CouldCan
Past tensePresent tense
Used to talk about an ability, something that was possible in the past, a possibility in the future, something that was generally permitted in the past; used to make a polite suggestion, request, or to ask a question politely; used to express a wish, a strong emotion, or an exaggerated feeling that makes the situation unrealistic; used to describe something that was possible but did not happen; used to describe a conditional situationUsed to describe an ability, possibility, impossibility (paired with “not”), or something that is allowed at present; used to ask for and give permission; used to make a suggestion or request