-거든요 vs -잖아요: New Information vs Shared Knowledge | Korean Grammar

There is a pair of Korean endings that sit in exactly the same slot, both address the listener directly, and both get translated into English as "you know" — and precisely because of that, English speakers pick between them by translation feel and get it wrong roughly half the time. The pair is -거든요 and -잖아요. They are not stylistic variants of one idea. They make opposite assumptions about who knows what, and swapping them doesn't just sound slightly off — it can make you sound like you're explaining the obvious, or reminding someone of something they never knew. This page exists to fix that confusion once and for all.

The one-sentence difference

-거든요 informs. -잖아요 reminds.

-거든요 = "here is something you do not know" — a reason, a background fact, a piece of the story you're supplying for the first time.
-잖아요 = "recall what you do know" — a fact already shared between you, pulled back into view.

Everything else follows from that. If you're the one bringing the fact to the table, it's -거든요. If you're pointing at a fact already on the table, it's -잖아요.

그 가게 문 닫았거든요.

geu gage mun dadatgeodeunyo

That shop has closed, just so you know. (I'm informing you)

그 가게 문 닫았잖아요.

geu gage mun dadatjanayo

That shop's closed, remember? (you already knew this)

Read those two aloud and feel the difference in the imagined listener. The first sentence is delivered to someone who is about to walk up to a closed shop — they don't know yet. The second is delivered to someone who was standing right next to you when you both saw the "closed" sign — you're just reactivating it.

The decisive diagnostic

When you're unsure which to use, ask yourself one question:

Could the listener already know this fact — and am I invoking it, or supplying it?

If they could already know it, and you're pointing back to it → -잖아요.
If they don't have it yet, and you're handing it over → -거든요.

왜 또 물어봐, 아까 설명했잖아.

wae tto mureobwa, akka seolmyeonghaetjana

Why are you asking again — I explained it already, remember. (shared: I told you, you should have it)

저 먼저 갈게요. 내일 일찍 일어나야 되거든요.

jeo meonjeo galgeyo. naeil iljjik ireonaya doegeodeunyo

I'll head out first — I have to get up early tomorrow, you see. (new: you didn't know my reason)

In the first, the speaker already gave the explanation, so its existence is shared — hence -잖아. In the second, the speaker's early morning is fresh news that justifies leaving — hence -거든요. Notice a very common pattern: -거든요 loves to answer an unspoken "why?" It hands over the reason behind something the listener has just noticed.

왜 안 먹어요? — 저 이거 못 먹거든요.

wae an meogeoyo? — jeo igeo mot meokgeodeunyo

Why aren't you eating? — I can't eat this, you see. (supplying the reason)

The minimal pair, held side by side

Take one neutral fact — "this is free" — and watch how the ending re-aims it at a different listener.

이거 원래 무료거든요.

igeo wollae muryogeodeunyo

This is actually free, you know. (you assumed you had to pay — I'm correcting you)

이거 원래 무료잖아요.

igeo wollae muryojanayo

This is free, remember? (we both already knew that)

The -거든요 version quietly corrects a wrong assumption; it's the ending you'd use to stop someone from reaching for their wallet. The -잖아요 version presumes you both know it's free and might even carry a faint "why are you acting surprised?" The words are identical except for the ending. The social scene is completely different.

These endings don't only carry information states — they carry attitude, and that's where a wrong choice does real damage.

Using -잖아요 where -거든요 belongs (i.e., for genuinely new info) implies the listener should have already known. It sounds presumptuous or faintly accusing — "come on, you knew this" — about something they had no way to know.
Using -거든요 where -잖아요 belongs (i.e., for a fact you both plainly share) sounds like you're needlessly explaining the obvious, or even talking down to them.

저 오늘 좀 예민하거든요. 이해해 주세요.

jeo oneul jom yeminhageodeunyo. ihaehae juseyo

I'm a bit on edge today, you see — please bear with me. (new info softening a request → -거든요)

우리 어제도 만났잖아요. 또 봐서 반가워요.

uri eojedo mannatjanayo. tto bwaseo bangawoyo

We met yesterday too, remember — nice to see you again. (shared memory → -잖아요)

Both feel warm and natural because the ending matches the knowledge state. Flip them — 저 오늘 좀 예민하잖아요 to someone who has no idea, or 우리 어제도 만났거든요 to the very person you met — and each turns subtly wrong: the first blames the listener for not knowing your mood, the second lectures them about a meeting they obviously remember.

English keeps these apart too — you just have to notice

English does distinguish these; the problem is that both can also be flattened to "you know," so learners lean on the ambiguous gloss. When you translate carefully, English uses different phrases:

-거든요 → "you see" / "just so you know" / "the thing is…" — these announce incoming information.
-잖아요 → "you know" / "come on" / "remember?" — these invoke existing information.

💡

Stop translating both as "you know." Retrain the pair as "you see" (거든요, new) versus "remember?/come on" (잖아요, shared). If your English paraphrase is "the thing is…" or "just so you know," you want -거든요. If it's "remember?" or "as you know," you want -잖아요. Choosing by knowledge state instead of by feel fixes the error at its root.

Register: don't drop the 요 with strangers

Both endings have bare 반말 forms — -거든 and -잖아 — used with close friends and juniors. With strangers, in service settings, or upward, keep the 요. This matters doubly for -잖아, whose "you knew this" force turns openly rude in bare form (see -잖아요's register warning), but even bare -거든 can read as clipped or cheeky with someone you've just met.

✅ 저 이거 못 먹거든요.

jeo igeo mot meokgeodeunyo

I can't eat this, you see. (polite — safe with anyone)

✅ 아까 말했잖아요.

akka malhaetjanayo

I did say so earlier, remember. (polite — pointed but not rude)

For more on when the bare intimate forms are licensed, see 반말 vs 존댓말.

Common Mistakes

Mistake 1: Choosing by the shared gloss "you know" instead of by knowledge state. This is the root error. New information you're supplying takes -거든요, not -잖아요.

❌ 사실 저 채식주의자잖아요.

Wrong if they don't know — you can't 'remind' someone you're vegetarian if you never told them.

✅ 사실 저 채식주의자거든요.

sasil jeo chaesikjuuijageodeunyo

Actually, I'm a vegetarian, you see. (new info → -거든요)

Mistake 2: Explaining the obvious with -거든요. When the fact is plainly shared, -거든요 sounds like you're lecturing.

❌ 왜 또 물어봐, 아까 설명했거든.

Off — you both know you explained it; recalling shared info wants -잖아, not -거든.

✅ 왜 또 물어봐, 아까 설명했잖아.

wae tto mureobwa, akka seolmyeonghaetjana

Why are you asking again — I explained it already, remember.

Mistake 3: Dropping 요 with someone you've just met. Both bare forms can offend; -잖아 especially.

❌ (처음 만난 사람에게) 저 이거 못 먹거든.

Too blunt with a stranger — keep the 요.

✅ 저 이거 못 먹거든요.

jeo igeo mot meokgeodeunyo

I can't eat this, you see.

Mistake 4: Forcing one ending to do both jobs. There is no neutral middle form. Diagnose the knowledge state first, then let the ending follow — that's the whole skill.

Key Takeaways

-거든요 informs (new information → "you see / the thing is"); -잖아요 reminds (shared information → "remember? / come on").
The decisive test: Could the listener already know this — am I invoking it (잖아요) or supplying it (거든요)?
-거든요 characteristically answers an unspoken "why," handing over a reason; -잖아요 pulls a shared fact back into view.
Wrong choice carries social cost: -잖아요-for-new sounds accusing; -거든요-for-shared sounds condescending.
Keep the 요 with strangers and superiors — bare -잖아 in particular turns rude.

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