Why Korean students say "Do you can swim?"
Korean marks ability by changing the verb ending, not by adding a helper word, so students double up and ask "Do you can swim?" Here's the simple reason, and drills that fix it in one class.
Park English2026-10-042 min read
Print it out
No sign-up, no email. Opens a clean print page.
A student raises her hand. "Teacher, do you can speak Korean?" You know what she means. You also know it's wrong, and you've heard the same sentence from twenty other students in twenty other classes.
This isn't a careless mistake. It comes straight from how Korean builds questions.
Why this happens
In English, "can" is a special word called a modal. It jumps to the front of the sentence to make a question: "Can you swim?" No "do" needed, because "can" already does that job.
Korean doesn't work this way. Ability is shown by changing the end of the verb itself, usually with 수 있다 attached after it. Questions are made by changing the sentence ending, not by moving a word to the front. There's no separate helper word sitting in front of the verb the way "can" does in English.
So when Korean students first learn English questions, they learn a rule that works for most verbs: add "do" to the front. "You like pizza" becomes "Do you like pizza?" That rule gets drilled hard, and it's reliable, until "can" shows up. Students treat "can" like any other verb, keep the "do" rule, and stack both: "Do you can swim?"
The fix isn't a long grammar explanation. It's showing them that "can" already is the question-mover, so "do" has no job left to do.
Teach it this way
Tell students: "Can" is a strong word. It doesn't need 'do' to help it. It can move to the front by itself.
Write both sentences on the board side by side:
| Wrong | Right |
|---|---|
| Do you can swim? | Can you swim? |
| Do she can cook? | Can she cook? |
| Do you can ride a bike? | Can you ride a bike? |
Have students read both out loud, then only the right side, three times each. Repetition fixes this faster than explanation at this age.
Drills, easy to hard
- Say it right. Teacher says a wrong sentence. Students fix it out loud. ("Do you can swim?" to "Can you swim?")
- Fill the blank. "___ you swim?" (Can) "___ you like pizza?" (Do)
- Build the question. Give word cards: you / swim / can. Students arrange them into a question with no extra words.
- Ask a friend. Students walk around asking three classmates "Can you ___?" using their own verb.
- Explain why. Stronger students try to say, in simple English, why "Do you can swim?" is wrong. This is the hardest step. Most will only manage "no do with can," and that's a correct answer.
The goal by the end of class isn't a perfect explanation. It's a student who hears "Do you can" out loud and winces a little, the same way they'd wince at a note that's slightly out of tune.