| Form | subject + can + base verb; one form for every subject | She can swim. |
| Negative | can't; the full form is cannot, one word | I can't swim. |
| Question | Can + subject + base verb; no do | Can you swim? |
| Ability | can for skills | I can cook pasta. |
| Permission | can allows, can't forbids; ask with Can I…? | You can park here. / Can I open the window? |
| Request | Can you…? asks for help | Can you help me, please? |
| A2Past ability | could for general ability in the past | I could run fast when I was young. |
| A2Polite request | Could is more polite than can | Could you open the door, please? |
| A2Possibility | could says what may happen | It could rain later. |
| A2Other tenses | be able to takes the place of can | I'll be able to help you tomorrow. |
| A2Trap | a single success in the past takes was / were able to | The fire was big, but we were able to escape. |