Learn Korean
Grammar Intermediate TOPIK II · Level 3–4 Intermediate Korean 1 · Unit 6

-으니

-으니: On Doing It, I Found That

Connective: prior fact as ground — often discovery after experiencing, also cause/premise.

Before this, make sure you know: -(으)니까 , -아서 / -어서 , -아요 / -어요

How to form it

When Form Example
Batchim stem (not ㄹ) -으니 먹으니 / 읽으니
Vowel or ㄹ stem -니 보니 / 가니 / 사니 (살다)
After past -었으니 봤으니 / 해 봤으니

-(으)니 links a prior fact to what follows. In this intermediate unit the star colour is discovery: after watching a film again for the first time in a while, you find it was really fun — the 보니… storytelling move.

우리말샘 lists cause/premise and “state one fact, then explain a related fact.” Classroom gloss leans discovery after doing/seeing, so learners do not flatten every instance into English because.

Forms

ㄹ drops (same family habit as -(으)니까):

보니          (보다)
가니          (가다)
먹으니        (먹다)
사니          (살다) — not *살으니
직접 해 보니 쉽더라고요.
설명을 들어 보니 이해가 됐어요.
모자를 써 보니 느낌이 달라요.
책을 읽어 보니 생각보다 재미있어요.

Discovery vs cold cause

창문을 열어 보니 바람이 차요.     on opening, I found…
비가 오니 집에 있을게요.         since/as it’s raining… (premise)
시간이 없으니 빨리 갑시다.       premise / ground

Both are real. This page trains the 보니… beat the unit leans on.

Versus -으니까 and -아서/어서

FormTypical classroom seat
-(으)니까spoken reason; OK before commands/suggestions
-(으)니discovery sequences; written-leaning cousin of -니까
-아서/어서everyday cause; never before commands
피곤하니까 쉬세요.     ✅
피곤해서 쉬세요.       ❌
피곤하니 쉬세요.       possible in some seats — learn -니까 as the safe command pattern

Not question -니?

-니? ends a banmal question (먹니?). Connective -(으)니 sits mid-sentence and continues.

영화 보니?              asking (banmal question ending)
영화 보니 재미있더라.    connective discovery

Ask: did doing or seeing X reveal Y? If yes, -(으)니 is a natural fit. If you only need everyday because before a request, prefer -(으)니까.

Do not confuse it with

-(으)니까

because (works before commands and suggestions)

-아서 / -어서

because (statement only, never a command)

-니?

casual question ending — intimate, gentle plain-style inquiry

Taught alongside this

On the jabi learning path, this appears in 오랜만에 영화를 보니 정말 재미있었어요 (It was really fun to see a movie after a long time.) — Intermediate Korean 1, Unit 6, on the theme of hobby. These come with it:

-나 보다 I guess — a guess from evidence, with verbs -는가 보다 the same guess, attached differently -은 결과 as a result of — the written summary phrase

Words used above

Tap the speaker to hear it read aloud by your browser.

-(으)니-(eu)nias / since / when I… (I found…)
보니boniwhen I looked / saw… (I found…)
발견balgyeondiscovery
전제jeonjepremise
문어muneowritten style

Quick check

No sign-up, no score saved — just see if it stuck.

1. 오랜만에 영화를 보니 재미있었어요 is closest to…

2. 살다 + this connective?

3. Safe form before a command?

Common questions

Is -(으)니 just formal -니까?

Related. -으니까 is often described as emphasising -으니. In practice -(으)니 also carries discovery sequences like 보니….

Can it mean because?

Yes — dictionary lists cause/premise. This Sejong gloss pushes the discovery colour so you do not translate every -(으)니 as bare because.

보니? as a question?

Different ending — ni-question. This page is the connective mid-sentence.

vs -아서/어서?

aseo-eoseo is the everyday cause/sequence workhorse. -(으)니 often feels tighter to ‘when I did X, Y became clear’ storytelling.