In this lesson, let us take a look at how to say “I’m not sure if …” in Korean. First of all, you need to remember that this is not going to be translated word for word.

“To be sure” and “to not be sure” in Korean
The word for “to be sure” or “to be certain” in Korean is 확실하다 [hwak-si-ra-da]. Therefore, the literal translation of “to not be sure” is 확실하지 않다 [hwak-si-ra-ji an-ta], but this form is not commonly used in everyday spoken Korean.

“Are you sure?”
When asking someone if they are sure or certain of something, you can still use the word 확실하다 and say “확실해요?” [hwak-si-rae-yo?]. Or, sometimes you can say “정말이에요?” [jeong-ma-ri-e-yo?] if you want to say “Are you serious?” or “Is that real?”.

How to say “I’m not sure”
The most natural Korean expression for “I’m not sure” is “잘 모르겠어요” [jal mo-reu-ge-sseo-yo]. The word 모르다 means “to not know” and if you say “잘 몰라요" it means “I don’t know well.” or “I don’t know much (about it).”

The suffix -겠- adds the nuance of assumption or intention (-겠- will be covered in more detail in a future lesson in Level 6.), so when you say 모르겠어요, you mean “I don’t seem to know” or “I would like to know, but I really don’t.”

잘 모르겠어요 means the same thing as 모르겠어요 because you don’t actually need the word “잘" there, but “잘 모르겠어요" is a common and fixed expression used by many Korean people to mean “I’m not sure” or “I don’t know for sure.”

How to say “I’m not sure if …”

“If or not” or “whether or not” in Korean is expressed through the structure -(으/느)ㄴ지 [-(eu/neu)n-ji] (Go back to Level 5 Lesson 18 to review).

-(으/느)ㄴ지 잘 모르겠어요 = I’m not sure if …
You can use interrogative words (when/what/where/how/who/why/which) with this structure, too.

Present Tense
= -(으/느)ㄴ지 잘 모르겠어요.

Ex)
이거 누구 책인지 잘 모르겠어요.
[i-geo nu-gu chae-gin-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure whose book this is.

Past Tense
= -았/었/였는지 잘 모르겠어요.

Ex)
다 끝났는지 잘 모르겠어요.
[da kkeut-nat-neun-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure if it all ended.

Future Tense
= -(으)ㄹ지 잘 모르겠어요.
= -(으)ㄹ 건지 잘 모르겠어요.

Ex)
서점이 내일 문을 열지 잘 모르겠어요.
[seo-jeo-mi nae-il mu-neul yeol-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure if the bookstore will open tomorrow.

And if you want to add “or not” at the end, you can use the structure Verb stem + -(으/느)ㄴ지 + Verb stem + 안 -(으/는)ㄴ지.

Sample Sentences
1. 어디로 갈지 잘 모르겠어요.
[eo-di-ro gal-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure where we will go.

2. 내일 만날지 안 만날지 잘 모르겠어요.
[nae-il man-nal-ji an man-nal-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure if we will meet tomorrow or not.

3. 여기가 맞는지 잘 모르겠어요.
[yeo-gi-ga mat-neun-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure if this is the right place.

4. 뭘 해야 될지 잘 모르겠어요.
[mwol hae-ya doel-ji jal mo-reu-ge-sseo-yo.]
= I am not sure what to do.
= I am not sure what I (will) have to do.

5. 이게 무슨 뜻인지 잘 모르겠어요.
[i-ge mu-seun tteu-sin-ji jal mo-reu-ge-sseo-yo.]
= I’m not sure what this means.