Korean -거든요 vs -잖아요: Explaining Yourself to a Friend
Korean -거든요 gives a reason your friend doesn't know yet (피곤하거든요), while -잖아요 reminds them of something you BOTH already know (약속했잖아요), remember?
Published:
Written by Alvin Lim Certified Korean Language Teacher (Level 2)
Korean -거든요 gives a reason your listener doesn’t know yet — 오늘 좀 피곤하거든요 (you see, I’m a bit tired today) — while -잖아요 reminds them of something you BOTH already know: 우리 약속했잖아요 (we promised, remember?). Both endings explain yourself, but they point in opposite directions: -거든요 hands over NEW information, -잖아요 leans on SHARED information. Getting that split right is the heart of natural Level-3 conversation.
When a friend asks for 조언 (advice) or wonders why you did something, you constantly toggle between these two. This lesson lives in those moments — explaining yourself, comforting a friend, and 털어놓다 (opening up) about what’s on your 마음.
Words for heart-to-heart talks
These come up the second a friend says “can I ask your advice?”
Telling them something they don’t know — -거든요
Use -거든(요) to hand over a reason or backstory the listener doesn’t have yet. It’s the “you see…”, the answer that supplies fresh information.
왜 일찍 가요? — 오늘 좀 피곤하거든요 = Why leaving early? — I’m a bit tired, you see 요즘 바쁘거든요, 그래서 연락을 못 했어요 = I’ve been busy, you see, so I couldn’t reach out 저 그 가수 좋아하거든요 = the thing is, I like that singer 어제 길을 걷고 있었거든요. 근데 갑자기… = so I was walking yesterday — and then suddenly…
The listener didn’t know the reason; -거든요 fills them in. It can answer a 왜? or kick off a story by laying down background. Notice the slightly confiding tone — you’re letting them in on something.
Reminding them of what you both know — -잖아요
-잖아(요) does the reverse: it points at information you both already share, nudging the listener to recall it. Think “remember?”, “you know how…”, “come on…”.
우리 어제 약속했잖아요 = we made a promise yesterday, remember? 그 영화 재밌잖아요, 같이 봐요 = that movie’s fun, you know it is — let’s watch it 내일 시험이잖아요. 공부해야죠 = there’s a test tomorrow, you know — gotta study 그 식당 비싸잖아요. 다른 데 가요 = that place is pricey, you know — let’s go elsewhere
Here you’re not delivering news — you’re reminding. Because it assumes “you already know this”, -잖아요 can sound pushy with strangers or seniors, so save it for friends and soften your tone. Among close friends, the casual -잖아 is warm and everyday.
Which one am I using?
The test is simple: does the listener already know it? If no → -거든요 (new). If yes → -잖아요 (shared). 피곤하거든요 introduces your tiredness; 약속했잖아요 recalls a promise you both made. Keep that question in mind and the two stop blurring together.
A friend talks it out
Watch both endings carry one little heart-to-heart:
See the contrast in action: 힘들거든 hands over the new reason behind the silence, and 우리 친구잖아 reminds you of the shared truth you both already accept. One supplies information, the other recalls it — and together they sound exactly like two friends talking.
FAQ
What’s the core difference between -거든요 and -잖아요? -거든요 delivers information the listener does NOT have yet — a fresh reason or backstory: 왜 안 왔어요? — 일이 있었거든요 = I had something come up (you didn’t know that). -잖아요 does the opposite: it reminds the listener of something you BOTH already know: 우리 약속했잖아요 = we promised, remember? So -거든요 answers “why?” with news, while -잖아요 nudges shared memory. Mixing them up sounds off: -거든요 for new info, -잖아요 for old.
Does -잖아요 ever sound rude? It can, if the ‘you already know this’ feels like scolding. 어제 말했잖아요 = I told you yesterday (so why are you asking?) may come across as impatient with a stranger or senior. Among close friends it’s warm and natural — 그거 맛있잖아 = come on, that’s tasty. To stay safe, use -잖아요 with people you’re comfortable with, soften your tone, and prefer plain explanations (-어서, -거든요) when reminding an elder or boss of something.
Can -거든요 start a story, not just answer a question? Yes. Beyond giving reasons, -거든요 often opens a story by laying down background the listener needs: 어제 길을 걷고 있었거든요. 근데 갑자기… = So I was walking yesterday, you see. And then suddenly… Here it doesn’t answer “why?” — it sets the stage and pulls the listener in, promising more to come. That “let me fill you in” feel is why -거든요 shows up so much in casual storytelling, not only in excuses.
Next: a proper apology — -느라고, -고 말다 and -어야겠다. Previous: campus life — 이고, -은 편이다 and -고 싶어 하다. Full path: curriculum hub.