Can or Could | The Difference Between Can and Could

Last updated on June 1, 2024 by Grammargeek

Understanding the difference between “can” and “could” is important for effective communication in English. These two modal verbs are commonly used when we’re talking about abilities, possibilities, and polite requests, but they’re not interchangeable. To use them correctly, we need to grasp their subtleties and apply them to the appropriate contexts.

Can or Could: What is the Main Difference?

CAN or COULD

Key Takeaways

In discussing proper usage, we want to ensure clarity and precision in our language. Here are the fundamental differences between “can” and “could”:

  • Can is used to express:
    • Physical or mental ability: We can swim.
    • Possibility: It can rain today.
    • Permission (informal): Can I borrow your pen?
  • Could is used to express:
    • Past ability: We could swim when we were young.
    • Polite requests: Could you tell us the time?
    • Possibility: It could snow tomorrow. (less certain than “can”)
    • Suggestion: We could try the new restaurant.

Definition and Usage

Can or Could | Ability

CAN is used to talk about the ability to do something at a given time in the present or future

  • He can speak Chinese fluently.

COULD is used to talk about past time

  • I could run 10 miles when I was young.

Can or Could | Request

COULD is used as a polite way of telling or asking someone to do something

  • Could you lock the door when you leave?

Can is more informal

  • Can you take me to the Victoria station?

Can or Could | Possibility

CAN is used to make general statements about what is possible

  • In Norway, temperatures can be low as -50°C in winter.

COULD is used to show that something is/was possible now or at a specific event in the past

  • The weather station said temperatures could be as low as -10°C tonight.

Can or Could | Asking Permission

CAN is used to ask for permission to do something in an informal way

  • Can I borrow your car tomorrow?

Could is more formal and polite than can

  • Could I choose my own doctor?

Can or Could | Talking about Things which Are Allowed

We use can to talk about things which are allowed in the present or future

  • You can take a holiday tomorrow if you want.

We use could to talk about things which were allowed in the past

  • When I first started this job we could take a holiday when we wanted.

Can or Could: Related Confused Words

Can vs Could

Can represent present or general ability. For example:

  • We can swim.
  • Can you help me?

In contrast, could often refer to past ability or a more tentative present possibility. For example:

  • We could swim when we were younger.
  • Could you help me, please?

Can vs May

Can denote ability, whereas May is typically used to express permission.

  • Can: We can finish the work by 5 PM.
  • May: May we leave the table?

However, “may” can also indicate a possibility, often in a more formal or polite context than “can.”

Could vs Might

Could and might both indicate the possibility, but there’s a slight difference in their usual contexts.

  • Could imply a possibility with a conditional or dependent aspect.
    • If we hurry, we could catch the train.
  • Might suggest a more uncertain possibility.
    • We might go to the beach this weekend, weather permitting.

Can or Could: Examples

Examples of “Can” 

  • I can swim very well.
  • She can speak three languages fluently.
  • We can see the stars tonight because the sky is clear.
  • He can solve complex math problems quickly.
  • They can come to the party if they finish their work on time.

Examples of “Could”

  • When I was younger, I could run for miles without getting tired.
  • She said she could help us with the project next week.
  • He could have won the race if he hadn’t injured his leg.
  • We could see the movie tomorrow if you’re free.
  • They could hear the music from the concert across town.

Interactive Quiz: “Can” vs. “Could”

Let’s assess our understanding of “can” and “could” with this interactive quiz.

  1. Which of the following is correct?
    • I can speak Spanish fluently.
    • I could speak Spanish fluently.
  2. Which of the following is correct?
    • When I was younger, I could run a mile in under six minutes.
    • When I was younger, I can run a mile in under six minutes.
  3. Which of the following is correct?
    • Could you please pass the salt?
    • Can you please pass the salt?
  4. Which of the following is correct?
    • She can’t come to the phone right now.
    • She couldn’t come to the phone right now.
  5. Which of the following is correct?
    • We could go to the beach this weekend if the weather is nice.
    • We can go to the beach this weekend if the weather is nice.

Answers

  1. I can speak Spanish fluently. (“Can” is used to express ability in the present.)
  2. When I was younger, I could run a mile in under six minutes. (“Could” is the past tense of “can” and is used to express ability in the past.)
  3. Both “Could you please pass the salt?” and “Can you please pass the salt?” are correct. (“Could” is more polite and “can” is more direct, but both are commonly used to make a request.)
  4. She can’t come to the phone right now. (“Can’t” is used for the present inability.)
  5. Both “We could go to the beach this weekend if the weather is nice.” and “We can go to the beach this weekend if the weather is nice.” are correct. (“Could” suggests a conditional possibility, while “can” indicates a more definite possibility assuming the condition of nice weather is met.)

Frequently Asked Questions

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

“Can” is used for expressing ability, permission, or possibility in the present tense. “Could” is often the past tense of “can” and is used for the same purposes in the past. However, “could” is also used to show a future possibility or to make polite requests in the present.

  • Ability: We can play piano. / We could play piano when we were younger.
  • Permission: Can I open the window? / Could I open the window?
  • Possibility: It can rain today. / It could rain tomorrow.

When should we use “could” to make a request?

We opt for “could” when we want to be more polite and indirect. For instance, “Could you pass the salt?” is politer than “Can you pass the salt?”

Is it acceptable to use “can” and “could” interchangeably?

While in casual conversation “can” and “could” might be used interchangeably to some degree, it’s important to use them correctly in formal writing or situations to convey the right tense and level of politeness.

Example:

  • Casual: Can/Could you help me with this?
  • Formal: Could you help me with this, please?

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