Can vs. Could: What's the Difference?
Learn how can and could express ability, permission, possibility, past time, and politeness, with examples, a quiz, and FAQs.
Can expresses present ability, permission, or a real possibility. Could expresses past ability, a conditional or less certain possibility, and often a more tentative request. Could is not always simply the past tense of can.
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A project lead asks, “Can you send the file today?” A more tentative “Could you send it today?” softens the request, but neither form guarantees that the deadline is optional.
Can vs. Could at a glance
| Word | Typical role | Meaning | Example |
|---|---|---|---|
| can | Modal verb | to be able, permitted, or possible now | I can review the draft this afternoon. |
| could | Modal verb | past ability, conditional ability, tentative possibility, or polite request | We could finish today if the data arrives by noon. |
How to use can
Use can for present ability, informal permission, offers, requests, and general possibility. Like other modal verbs, it takes the base form without to: can read, can help, and can be.
I can review the draft this afternoon.
How to use could
Use could for general ability in the past, hypothetical outcomes, possible options, and softened questions. For one successful action on a particular past occasion, managed to or was able to may be clearer.
We could finish today if the data arrives by noon.
Rules that make the choice easier
Use can for present capability
Choose can when someone has the ability or opportunity now: “She can access the account.”
Use could for conditions and options
Could often appears with if or presents one possible course: “We could wait if the train is delayed.”
Use either carefully in requests
Can you and could you both make requests. Could you is often more tentative or polite, but tone also depends on context.
Common mistakes to avoid
- Do not add to after the modal: write can go and could go, not can to go.
- Do not assume could always refers to the past.
- Avoid could of; the correct perfect form is could have or could've.
Quick practice
1. She ___ swim by age five.
Answer: could
2. I ___ meet you now.
Answer: can
3. We ___ leave early if the work is done.
Answer: could
Frequently asked questions
What is the difference between can and could?
Can is more direct and current; could often marks past ability, condition, tentativeness, or politeness.
Is could the past tense of can?
It can express past ability, but it also has conditional and tentative uses that are not past tense.
Is could you more polite than can you?
It is often perceived as more tentative, though both are standard requests.
Is could of correct?
No. Write could have or the contraction could've.