Present ability: can / can't
| Form | Example |
|---|---|
| can + infinitive | She can speak four languages. |
| can't + infinitive | I can't see the board from here. |
| Can + subject + infinitive? | Can you drive? |
CAN for typical behaviour:
Can also describes what someone typically does: "John can be quite rude at times." (= he sometimes is rude)
Past ability: could vs was/were able to
| Form | Use | Example |
|---|---|---|
| could | General ability in the past (over time) | When I was young, I could run very fast. |
| could | Ability with perception verbs (see, hear, feel, smell) | I could see the mountains from my window. |
| was / were able to | Managed to do on one specific occasion | The fire was serious, but the firefighters were able to save everyone. |
| couldn't / wasn't able to | Inability (both work for general & specific) | I couldn't find a taxi anywhere. |
He could play chess as a child. (general)
The match was difficult, but she was able to win in the end. (one occasion)
✓ Both: "I couldn't / wasn't able to sleep last night."
The match was difficult, but she was able to win in the end. (one occasion)
✓ Both: "I couldn't / wasn't able to sleep last night."
Special uses
| Expression | Meaning & Example |
|---|---|
| can't help + -ing | Unable to stop yourself doing something I can't help laughing — the joke was so funny! |
| couldn't help + -ing | Same, in the past She couldn't help crying at the end of the film. |
| could + infinitive (conditional) | Polite suggestion or request We could go to the cinema tonight. |
Exercises
could or was/were able to?
1. When I was ten, I ___ swim across the whole pool.
2. The exam was really hard, but she ___ pass in the end.
3. From my bedroom I ___ hear the traffic outside.
4. The road was blocked, but we ___ find another route.