-고 보니

Build it

When to use it

Attach -고 보니 to a verb stem — no vowel rule, ㄹ stays, no tense in front. 보니까 is the fuller form.

The first action must be completed, and the second clause reports what you found out as a result: 사고 보니 크기가 맞지 않았다.

The subject is the same for both clauses — you did the thing, and you made the discovery.

Very often the discovery is unwelcome, though it need not be. What is fixed is that you could not have known beforehand.

How to attach it

In use

1. 사고 보니 크기가 맞지 않았어요.

   Having bought it, I found the size was wrong.

2. 말하고 보니 실수였다는 걸 깨달았다.

   Once I’d said it, I realised it had been a mistake.

3. 도착하고 보니 아무도 오지 않았더라고요.

   When I got there I found nobody had come.

4. 알고 보니 서로 아는 사이였다.

   As it turned out, they already knew one another.

5. 직접 만들고 보니 생각보다 어렵지 않았다.

   Having made it myself, I found it was not as hard as I’d thought.

6. 읽고 보니 예전에 본 책이었어요.

   Once I’d read it, I realised it was a book I’d seen before.

Compared with

• -다 보니

  The pair to keep straight. -고 보니 follows one completed action; -다 보니 follows repeated or continued action.

  먹고 보니 상한 거였다. (ate it, then found out)  /  먹다 보니 입에 맞더라. (kept eating, grew to like it)

• -았/었더니

  더니 reports what happened as a consequence of your action; 고 보니 reports what you found to be true all along.

  전화했더니 안 받더라. (I rang and he didn’t answer)  /  전화하고 보니 번호가 틀렸다. (I found the number was wrong)

• 알고 보니

  Worth learning as a set phrase. 알고 보니 means “as it turns out” and introduces a revelation.

  알고 보니 형제였다.  /  알고 보니 오해였어요.

Watch out

• 계속 먹고 보니 입에 맞더라고요.

  계속 먹다 보니 입에 맞더라고요.

  Continued action takes -다 보니. -고 보니 follows one completed action.

• 제가 사고 보니 동생이 실망했어요.

  제가 사고 보니 크기가 맞지 않았어요.

  The discovery belongs to the same person who acted. Someone else’s reaction needs a separate clause.

• 샀고 보니 크기가 맞지 않았어요.

  사고 보니 크기가 맞지 않았어요.

  -고 never carries tense here. The past goes on the final verb.

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