-지만 vs -는데: Korean's two "but"s aren't the same

If your textbook told you that both -지만 and -는데 mean "but," it wasn't lying — but it left out the part that matters. Here's the one idea to take away:

-지만 is a contrast. -는데 is a setup.

-지만 says: this is true, and the next thing goes against it. -는데 says: here's the situation — now listen to what I'm about to say. Sometimes that situation happens to contrast with what follows, which is why "but" works as a translation. Often it doesn't contrast at all, and "but" is simply wrong.

Once you feel that difference, a lot of your Korean will suddenly sound less like a textbook.

The forms first

-지만 is easy: it attaches straight to the stem, no vowel-checking.

-는데 changes depending on what kind of word it follows. This is where most mistakes happen.

Two traps: 좋다 and 많다 are adjectives, so it's 좋은데, 많은데 — never 좋는데. But 있다/없다 behave like verbs here: 재미있는데, 시간 없는데. And in the past tense everything becomes -는데, so you never have to think about it.

-지만: a real contrast

Use -지만 when the second clause genuinely pushes against the first. You could put although in front of the first clause in English and it would still make sense.

• 이 가방은 예쁘지만 너무 비싸요. — This bag is pretty, but it's too expensive.
• 김치는 맵지만 맛있어요. — Kimchi is spicy, but it's delicious.
• 저는 한국에 살지만 한국 사람은 아니에요. — I live in Korea, but I'm not Korean.
• 표를 샀지만 못 갔어요. — I bought a ticket, but I couldn't go.

-지만 also feels a bit more written and a bit more formal. In essays, announcements and news writing it's everywhere. In casual speech Koreans use it too, but less often than learners do.

-는데: background before the point

-는데 hands the listener a piece of context and then delivers the real message. The second clause can contrast, explain, ask, or request — -는데 doesn't care.

Context, then the main news:

• 어제 그 영화 봤는데 진짜 재미있었어요. — I saw that movie yesterday and it was really good.
• 주말에 부산에 가는데 같이 갈래요? — I'm going to Busan this weekend — do you want to come?

Notice you can't say "but" in either of those. That's -는데 doing its real job.

Softening a request or a refusal:

• 죄송한데 여기 자리 있어요? — Sorry, is this seat taken?
• 지금 좀 바쁜데 나중에 얘기해도 돼요? — I'm a little busy right now — can we talk later?
• 그 색깔도 좋은데 다른 색은 없어요? — That color is nice too, but do you have another color?

Contrast (yes, it does this too):

• 아까 전화했는데 안 받으시더라고요. — I called earlier but you didn't pick up.
• 날씨는 좋은데 좀 추워요. — The weather is nice, but it's a bit cold.

All of these are 해요체 — everyday polite speech, which is where -는데 lives most comfortably.

The nuance natives feel

Here's the test I'd give a student: can you replace the connector with 그렇지만 ("however") and still sound sane? If yes, -지만 fits. If what you really mean is closer to 그런데 ("so anyway, here's the thing"), use -는데.

Compare:

• 어제 그 책 읽었는데 너무 좋았어요. ✅ I read that book yesterday and it was great.
• 어제 그 책 읽었지만 너무 좋았어요. ❌

The second sentence isn't ungrammatical — it's just strange. To a Korean ear, -지만 promises a reversal, so 읽었지만 sets up something like "…but I didn't understand it." Then "it was great" arrives and the listener has to mentally back up. It's like saying in English, "Although I read that book, it was great." Technically parsable. Nobody talks like that.

The other thing: -는데 is polite because it's indirect. Starting with context instead of a demand gives the listener room to move. Compare these two ways of asking a shop assistant for help:

• 다른 사이즈 주세요. — Give me another size. (fine, but blunt)
• 이거 조금 작은데 다른 사이즈 있어요? — This is a bit small — do you have another size? (natural, soft)

That second pattern is one of the most useful things in spoken Korean. A huge share of real requests begin with a -는데 clause.

And -는데 can even end the sentence, trailing off to imply the rest:

• 이거 좀 비싼데요. — This is a little pricey… (= so I'd rather not)
• 지금은 좀 어려운데요. — That's a bit difficult right now… (a soft no)

That final -요 keeps it polite. Without it (비싼데…) it's 반말, for friends only.

Common mistakes

1. 좋는데, 많는데, 바쁘는데 — adjectives take -ㄴ/은데. Say 좋은데, 많은데, 바쁜데.

2. Using -지만 for everything. Learners reach for -지만 because it has one form. The result sounds stiff and sometimes accidentally argumentative. When you're just giving background, switch to -는데.

3. Building the past tense by hand. The error is 가았는데 or 갔은데. Past + -는데 is always -았/었는데: 갔는데, 먹었는데, 좋았는데.

4. 죄송하지만 vs 죄송한데. Both exist and both are correct. 죄송하지만 is the more formal, set phrase (announcements, customer service, 합쇼체 contexts). 죄송한데 is what you say to a stranger on the street. Use whichever matches the room.

Quick decision guide

Practice

1. Conjugate: 시간이 없다 + -는데 → ?
2. Conjugate: 어제 친구를 만나다 (past) + -는데 → ?
3. Which is natural? (a) 어제 카페에 갔지만 사람이 많았어요. (b) 어제 카페에 갔는데 사람이 많았어요.
4. Fix the mistake: 날씨가 좋는데 밖에 나갈까요?
5. Say it in Korean (해요체): "I'm a little busy right now — can we talk later?"

Answers

1. 없는데 (있다/없다 take -는데)

2. 만났는데 (past tense is always -았/었는데)

3. (b) 어제 카페에 갔는데 사람이 많았어요. — It's background, not a contradiction. (a) makes the listener expect a reversal that never comes.

4. 날씨가 좋은데 밖에 나갈까요? — 좋다 is an adjective, so -은데.

5. 지금 좀 바쁜데 나중에 얘기해도 돼요? (Also fine: 지금 좀 바쁜데 이따가 얘기할까요?)

One small habit to build this week: every time you're about to ask a Korean speaker for something, start with a -는데 clause. 저기요, 길 좀 물어보려고 하는데요. It's a tiny change, and it makes you sound considerably more fluent than your vocabulary says you are.