Can means you know how to do something (ability), or that something is possible: I can swim = I know how to swim. We can start now = it's possible now. We also use Can you...? / Can I...? to ask someone for help or permission: Can you help me?Can I sit here?
What can means
I can ride a bike. = I know how to ride a bike.
It's sunny, so we can play outside. = it's possible.
Can you open the door? = asking for help.
Not "I can swim. = I want to swim." — say "I can swim. = I know how to swim.". Can is about ability or possibility, not wanting.
Try it: Camila says, "I can cook." What does she mean? (She knows how to cook. / She wants to cook. / She must cook.) Answer: She knows how to cook. — Can shows ability or possibility. "I can cook" means she knows how to do it — not that she wants to or has to.
Try it: You need help. Which sentence asks someone for help? (Can you help me? / I can help you. / You can help.) Answer: Can you help me? — We use Can you...? to ask someone for help. "Can you help me?" is a request. The others just say that someone is able to help.
can + base verb
To make can, use can + the base verb. No to, no -ing.
I can swim.
She can drive.
They can help you.
Not "I can to swim." — say "I can swim.". Nothing goes between can and the verb, no to.
Try it: Diego ___ at Farrisen Gym. (can swim / can to swim / can swimming) Answer: can swim — After can, use the base verb on its own: can swim. No "to" and no "-ing" after can.
Same for everyone (no -s)
Can never changes. He, she, it use can too, no -s.
I can cook.
She can cook.
They can cook.
Not "She cans cook." — say "She can cook.". Even with she, it stays can, never cans.
Try it: Camila ___ really well. (can cook / cans cook / can cooks) Answer: can cook — Can never takes -s, and the verb after it stays plain too: Camila can cook (not "cans" or "cooks").
Negative: can't
For not, use can't + the base verb. The full form is cannot (one word).
I can't swim.
He can't drive.
We cannot come today. = We can't come today.
Not "I don't can swim." — say "I can't swim.". The negative of can is can't, not 'don't can'.
Try it: Sorry, I ___ today. (can't come / don't can come / can't to come) Answer: can't come — The negative of can is can't, followed by the base verb: I can't come (not "don't can" and no "to").
Questions: Can first
To ask, put Canbefore the person, then the base verb.
Can you swim?
Can she drive?
What can I do?
Not "Do you can swim?" — say "Can you swim?". For a question, Can goes first, you don't need 'do'.
Try it: ___ you help me with this? (Can / Do can / Are) Answer: Can — Start the question with Can, before the person: Can you help me? You don't add "do" before can.
Try it: Remember what follows can, Lani ___ a bike. (can ride / can rides / can to ride) Answer: can ride — After can, always the base verb: can ride. (No -s, no "to", no "-ing", every time.)