Key Facts
- Hangul: 이유; Revised Romanization: iyu
- Part of speech: noun
- Origin: Sino-Korean, hanja 理由 (理 reason + 由 cause)
- Register: Neutral and common.
Reason in Korean: What Does 이유 Mean?
이유 means reason or cause. It is Sino-Korean, neutral and very common. It names the reason as a thing, so it is used in questions and in noun phrases about why something happened.
How Do You Pronounce 이유?
Two syllables, i-yu, with no sound changes. The vowel in 유 sounds like "you". Both syllables get the same weight, and nothing is tensed or linked, so you say it as written.
Example Sentences with 이유
이유가 뭐예요?
Iyuga mwoyeyo?
What is the reason?
The basic why question in noun form. 뭐예요 means what is it, so the sentence asks directly for the reason.
늦은 이유를 말해 주세요.
Neujeun iyureul malhae juseyo.
Please tell me the reason you were late.
Here 이유 follows a clause, 늦은, meaning late. 말해 주세요 asks someone to tell you, which makes it polite.
특별한 이유 없이 그냥 왔어요.
Teukbyeolhan iyu eopsi geunyang wasseoyo.
I came without any special reason.
특별한 means special. 없이 means without. The sentence says nothing in particular brought me here.
Common Phrases and Collocations
Three fixed phrases with 이유 cover asking, lacking and giving a reason.
| Korean | Meaning |
|---|---|
| 이유를 묻다 | to ask the reason |
| 이유가 없다 | to have no reason |
| 그런 이유로 | for that reason |
The Mistake to Avoid
Wrong: dropping 이유 between two clauses as if it were the word "because".
Correct: join two clauses with a connector such as -(으)니까 or -아서. Use 이유 as a noun, with a describing phrase before it, as in 늦은 이유 (the reason you were late).
이유 Compared with Similar Words
Three words overlap with 이유, each with its own tone.
| Word | Meaning | How it differs |
|---|---|---|
| 이유 | reason | This page's word |
| 원인 | cause | The cause of an event, more technical. |
| 까닭 | reason (native) | Literary tone. |
| 때문 | because (noun) | Used in ~ 때문에, "because of"; it links a cause to the sentence. |
At the Station: Explaining a Late Arrival
Two classmates are meeting to travel together. One arrives late and apologizes. The other asks what happened, then accepts the explanation. This exchange gives a reason without turning the noun 이유 into a word meaning “because”.
Classmate A
늦어서 미안해요.
Neujeoseo mianhaeyo.
Sorry I am late.
Classmate B
늦은 이유가 뭐예요?
Neujeun iyuga mwoyeyo?
What is the reason you are late?
Classmate A
버스를 놓쳤어요.
Beoseureul nochyeosseoyo.
I missed the bus.
Classmate B
괜찮아요. 다음 기차를 타요.
Gwaenchanayo. Daeum gichareul tayo.
It is okay. Let’s take the next train.
늦은 이유 names “the reason for being late”. The answer gives the event directly: missing the bus. It does not need to repeat 이유 to count as an explanation. 다음 기차 means the next train, so the final line moves the conversation from the cause of the delay to a practical plan.
Build a Phrase around 이유
이유가 있다 means there is a reason, and 이유가 없다 means there is no reason. 가 marks the reason as the thing that exists or does not exist. In 이유를 묻다, “to ask the reason”, 를 marks what someone asks about. The particle changes with the role of the noun.
이유를 설명하다 means to explain the reason. 설명하다 is useful when an answer needs detail, such as why a plan changed. 이유를 말하다 simply means to tell or state the reason. Both phrases treat 이유 as something you can ask about or explain.
그런 이유로 means “for that reason” or “for reasons like that”. 로 links the reason to the following outcome. The phrase looks back to an explanation already given, so a listener normally needs that earlier context to know what “that” refers to.
특별한 이유 없이 means “without any special reason”. In the existing example, it pairs with 그냥, “just”, to describe a visit without a particular purpose. The phrase softens the idea that every small action needs an elaborate explanation.
Asking Why without Sounding Accusatory
이유가 뭐예요? is grammatically polite, but it can still sound direct. A friend asking about a choice and a manager questioning a mistake may use the same words with different tones. The polite ending does not by itself make a personal question gentle.
혹시 이유를 알 수 있을까요? means “May I ask the reason?” More literally, it asks whether the speaker could know it. 혹시 makes the approach tentative, and the question leaves room for a careful reply. It can suit a customer-service conversation about a cancellation or a changed arrangement.
A short 왜요? means “Why?” In a relaxed exchange it can be simple curiosity; after a disagreement it can sound challenging. Use the situation and your relationship to decide how much explanation to put into the question.
Where Will You Read 이유?
Forms may ask for a 취소 이유, “reason for cancellation”, or a 지원 이유, “reason for applying”. The word before 이유 identifies the action being explained. In a form field, these compact noun phrases can appear without a full question.
News and discussions use 이유 to explain decisions or behavior. 원인 is useful when the focus is an event’s cause, such as what produced a fault. 이유 can also concern a person’s thinking: why they chose one course or product. The two words overlap, but the focus helps you choose.
Words for Following an Explanation
| Korean | Meaning | A useful connection |
|---|---|---|
| 왜 | why | Ask directly about a reason. |
| 원인 | cause | Focus on what produced an event or problem. |
| 결과 | result | Name what happened after the cause or decision. |
| 목적 | purpose | Name what an action aims to achieve. |
The reasoning words lesson groups these ideas. 목적 points toward an intended goal, while 이유 explains why someone acts or why something happened. That difference helps when a question asks for your purpose rather than the cause of a problem.
Quick Self-Test
- In 이유를 묻다, what does 를 mark?
- Does a polite ending guarantee that 이유가 뭐예요? sounds gentle?
- Which word points to an intended goal: 결과 or 목적?
Show answers
- The thing being asked about: the reason.
- No. Tone, situation and the relationship also affect how direct it sounds.
- 목적 means purpose. 결과 means result.
Frequently Asked Questions
How do you say reason in Korean?
Say 이유 (iyu).
How do you ask for the reason?
Say 이유가 뭐예요?
How do you say for that reason?
Say 그런 이유로.
Is 이유 the same as 원인?
Not quite. 원인 is cause and is more technical.
Related Words and What to Learn Next
- Theme list: Korean reasoning words groups 이유 with its neighbours.
- Index: Korean words A to Z lists every single-word page.
- Practice: put 이유 into the vocabulary flashcard decks.
- Next in the list: the page for result.