Two uses of Can
Can is a modal verb. It has two main uses: ability (things you know how to do) and permission (things that are allowed). Both use the exact same form — context tells you which meaning is intended.
Ability
Skills you have.
She can speak three languages.
Inability
Skills you don’t have.
I can’t swim. (= don’t know how)
Permission
Asking if allowed.
Can I sit here?
Requests
Asking someone to do something.
Can you help me?
Formula — Super Simple!
The golden rule of modal verbs
Subject+can+verb (always base form)
can NEVER changes: I can / he can / they can — same for everyone. No -s, no -ing, no -ed.
❌ Negative
Subject+can’t / cannot+verb (base)
❓ Question
Can+subject+verb (base)?
Answer: Yes, I can. / No, I can’t. (NOT: Yes, I can swim.)
Examples
I can play the guitar.
Ability — I know how
He can’t drive yet.
Inability — doesn’t know how
Can you open the window?
Request
Can I use your phone?
Asking for permission
✗ Wrong
She cans speak French.
Can never takes -s!
✓ Correct
She can speak French.
can = same for everyone
✗ Wrong
I can to swim.
After can → base form, no “to”
✓ Correct
I can swim.
can + base form (no “to”)
💡 Memory Hack
Can is a robot — it never changes
Think of can as a robot that always looks and sounds the same. It doesn’t care who is speaking — I can, she can, they can, we can. No -s, no to, no changes. Ever. The verb after it stays in base form too: can swim, can’t run, can speak.