When speaking Korean, it’s important to express not only what you know but also what you’re unsure about. One useful grammar pattern for this is ‘-았/었을지도 모르다’, which helps you talk about something that possibly happened in the past. In this post, you’ll learn how to use ‘-았/었을지도 모르다’ naturally with real-life examples and simple explanation
Contents
1. Definition
‘-았/었을지도 모르다’ is used to express that something might have happened or could have been the case in the past. It shows possibility with uncertainty.
Equivalent in English: might have, could have, may have
2. Form (Structure)
Structure:
- Verb stem + 았/었 + 을지도 모르다
- Action or event you are uncertain about in the past.
- Example: 가다 (to go) → 갔을지도 모르다 (might have gone)
- Adjective stem + 았/었 + 을지도 모르다
- Past state or quality you are unsure about.
- Example: 크다 (to be big) → 컸을지도 모르다 (might have been big)
- Noun + 이었/였 + 을지도 모르다
- Speculation about a past state or identity described by a noun.
- ‘이었’ attaches if noun ends with a consonant, ‘였’ if ends with a vowel.
- Example: 실수 (mistake) → 실수였을지도 모르다 (might have been a mistake)
- Example: 학생 (student) → 학생이었을지도 모르다 (might have been a student)
Notes:
- The ending -았/었 changes depending on the vowel harmony in the verb or adjective stem (past tense marker).
- The phrase 을지도 모르다 literally means “might have” or “may have,” expressing uncertainty or speculation.
- The noun copula ‘이다’ requires past tense ‘이었/였’ before adding ‘을지도 모르다.’
Table: Structure Summary
| Rule Type | Type | Example |
| (verbs/adjectives) Ends with ㅏ or ㅗ | 가다 (to go) 빠르다 (to be fast) | 갔을지도 모르다 (might have gone) 빨랐을지도 모르다 (might have been fast) |
| (verbs/adjectives) Others | 먹다 크다 (to be big) | 먹었을지도 모르다 (might have eaten) 컸을지도 모르다 (might have been big) |
| 하다 verbs | 하다(to do) | 했을지도 모르다 (might have done) |
| (verbs/adjectives) Negative form | 안 먹다 / 먹지 않다 (to not eat) | 안 먹었을지도 모르다 (might not have eaten) 먹지 않았을지도 모르다 (might not have eaten) |
| Nouns | 학생 (student) 간호사 (nurse) | 학생이었을지도 모르다 (might have been a student) 간호사였을지도 모르다 (might have been a nurse) |
3. Meaning & Usage
1. To Express Uncertainty About a Past Event
Use this structure when you are unsure about what happened in the past.
- 어제 그 사람이 집에 있었을지도 몰라요.
He might have been at home yesterday. - 시험이 어려워서 많이 틀렸을지도 몰라요.
I might have gotten a lot wrong because the test was hard. - 친구가 늦잠을 잤을지도 몰라요.
My friend might have overslept. - 정류장을 지나쳤을지도 몰라요.
He might have passed the bus stop. - 이미 출발했을지도 몰라요.
They might have already left.
2. To Make a Polite or Careful Guess About Someone’s Past Situation
This expression allows you to gently speculate or politely guess about someone’s situation in the past.
- 힘든 일이 있었을지도 모르겠네요.
Maybe something difficult happened to them. - 어제 많이 피곤했을지도 모르겠어요.
She might have been very tired yesterday. - 실수였을지도 모르죠.
It might have been a mistake. - 무서워서 말을 못 했을지도 몰라요.
He might not have spoken out of fear. - 도와주고 싶었을지도 몰라요.
She might have wanted to help.
3. To explain a possible cause or reason for a current situation
Use this form when you want to suggest a possible reason for something happening now.
- 비가 와서 도로가 미끄러웠을지도 몰라요.
(It might have been slippery because it rained.) - 뭔가를 잘못 눌렀을지도 몰라요.
(You might have pressed something wrong.) - 전화기를 꺼놨을지도 몰라요.
(He might have turned off his phone.) - 약속을 잊었을지도 몰라요.
(She might have forgotten the appointment.) - 길을 잘못 들었을지도 몰라요.
(We might have taken the wrong road.)
4. To Reflect on Your Own Possible Mistake or Action
This form is often used to reflect on something you might have done (or failed to do) in the past.
- 제가 말을 너무 빨리 했을지도 몰라요.
I might have spoken too fast. - 주소를 잘못 썼을지도 몰라요.
I might have written the wrong address. - 메일을 안 보냈을지도 모르겠네요.
I might not have sent the email. - 예약을 취소 안 했을지도 몰라요.
I might not have canceled the reservation. - 돈을 덜 냈을지도 몰라요.
I might have underpaid.
5. To Soften Criticism or Blame
This grammar helps soften criticism by suggesting the possibility that something was not intentional or definite.
- 그 사람도 이유가 있었을지도 몰라요.
Maybe he had his reasons. - 실수였을지도 모르잖아요.
It could have been just a mistake. - 몰랐을지도 모르죠.
They might not have known. - 바빠서 잊었을지도 몰라요.
She might have forgotten because she was busy. - 착각했을지도 모르겠네요.
He might have been confused.
4. Key Points to Remember
- Only used for events or situations in the past. This grammar is not used to talk about the present or future.
- Expresses uncertainty, speculation, or possibility about past events. It is great for guessing or showing that you’re not sure.
- Can be softened further with endings like -겠네요, -죠, -겠어요 to sound more polite or tentative.
- Not used for definite facts. If you know something happened for sure, do not use this structure.
- Commonly used in polite or indirect speech, but also natural in everyday conversation.
5. Practice Exercises
Fill in the blanks with the correct form of ‘-았/었을지도 모르다’.
- 어제 너무 피곤해서 숙제를 안 (하다) __________.
(You might not have done your homework because you were tired yesterday.) - 친구가 전화를 못 받았어요. 아마 (자다) __________.
(My friend didn’t answer the phone. He might have been sleeping.) - 문을 (안 잠그다) __________.
(You might not have locked the door.) - 그 사람을 길에서 (보다) __________.
(You might have seen that person on the street.) - 선생님이 회의 중이었어서 (바쁘다) __________.
(The teacher might have been busy.) - 이메일을 (잘못 보내다) __________.
(You might have sent the email to the wrong address.) - 약속 장소를 (착각하다) __________.
(He might have mistaken the meeting place.) - 컴퓨터가 (고장 나다) __________.
(The computer might have been broken.) - 제가 설명을 충분히 (안 하다) __________.
(I might not have explained enough.) - 시험 날짜를 (헷갈리다) __________.
(You might have confused the exam date.)
6. Answers
- 안 했을지도 모르다
- 잤을지도 모르다
- 안 잠갔을지도 모르다
- 봤을지도 모르다
- 바빴을지도 모르다
- 잘못 보냈을지도 모르다
- 착각했을지도 모르다
- 고장 났을지도 모르다
- 안 했을지도 모르다
- 헷갈렸을지도 모르다
7. Common Mistakes and Tips
⚠️ Mistake 1: Using present tense with ‘-았/었을지도 모르다’
Incorrect: 지금 비가 올지도 모르다. ❌ (It might be raining now.)
Correct: 아까 비가 왔을지도 몰라요. ✅ (It might have rained earlier.)
💡 Tip: ‘-았/었을지도 모르다’ is used only for past events. For present or future speculation, use ‘-ㄹ/을지도 모르다’.
⚠️ Mistake 2: Using it for confirmed past facts
Incorrect: 어제 친구를 만났을지도 몰라요. ❌ (I might have met my friend yesterday.)
Correct: 어제 친구를 만났어요. ✅ (I met my friend yesterday.)
💡 Tip: Use simple past tense to state definite facts. Only use ‘-았/었을지도 모르다’ when you are uncertain about the event.
⚠️ Mistake 3: Using it with adjectives incorrectly
Incorrect: 맛있었을지도 몰라요 음식. ❌ (The food might have been delicious.)
Correct: 음식이 맛있었을지도 몰라요. ✅ (The food might have been delicious.)
💡 Tip: Always maintain proper Korean sentence word order, even in speculative or uncertain expressions.
The Korean grammar pattern ‘-았/었을지도 모르다’ helps express uncertainty or possibility about past events. It’s especially useful in polite conversation, when you want to avoid making definite statements. Mastering this form will help learners sound more natural and thoughtful in Korean.