Can, Could and (be) able to
Expressing ability in the present, past, and other tenses
Can: Possibility, Permission, and Ability
Use can to say that something is possible, that somebody is allowed to do something, or that somebody has the ability to do something. Can is followed by the infinitive without “to.”
- We can see the warehouse from our office window.
- “I forgot my badge.” “You can use the side entrance — I’ll let you in.”
- *Can you speak any foreign languages?*
- I can come to the meeting tomorrow if you like.
The negative is can’t (= cannot):
- I’m afraid I can’t attend the conference on Friday.
Can vs. (Be) Able To
You can say that somebody is able to do something, but can is more usual:
- We are able to see the warehouse from our office. (= We can see …)
Can has only two forms: can (present) and could (past). When you need other tenses or verb forms, use (be) able to.
| can | (be) able to |
|---|---|
| I can’t sleep. | I haven’t been able to sleep recently. |
| Tom can come tomorrow. | Tom might be able to come tomorrow. |
| Maria can speak French and English. | Applicants must be able to speak two foreign languages. |
Could: Past of Can
Sometimes could is the past of can. Use could with verbs of perception and mental state: see, hear, smell, taste, feel, remember, understand.
- We had a great room at the hotel. We could see the lake.
- As soon as I walked into the office, I could smell something burning.
- I was sitting at the back of the conference room and couldn’t hear very well.
Could also says that somebody had a general ability or was allowed to do something:
- My old manager could speak five languages.
- We were given full access. We could do what we wanted.
Could vs. Was/Were Able To
Use could for general ability in the past:
- My old manager could speak five languages.
- I could see them from the window, but not very clearly.
But when somebody succeeded in doing something in a specific situation, use was/were able to or managed to (not could):
- The system crashed, but the IT team was able to recover all the data. (not
could recover) - I didn’t know where the file was, but I managed to find it in the end. (not
could find)
Compare general ability with a one-time success:
| General ability (could) | Specific success (was able to / managed to) |
|---|---|
| He was an excellent negotiator. He could close any deal. | The negotiation was tough, but he managed to close the deal. |
The negative couldn’t works in all situations — both general ability and specific situations:
- My old manager couldn’t swim.
- I looked everywhere for the report, but I couldn’t find it.
- She prepared well, but she couldn’t pass the certification exam.
Quick Self-Check
Sarah has travelled a lot. She _____ speak four languages.
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I haven't _____ sleep well recently because of the deadline pressure.
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The server went down, but the engineers _____ fix it before the client presentation.
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When I entered the meeting room, I _____ hear people arguing in the next office.
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Ask the IT department about your problem. They might _____ help you.
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