Conditionals in Korean: 면, 거든, 다면, 아/어야

Core examples: 시간이 있으면; 문제가 생기거든; 내가 부자라면; 공부해야 합격한다; 비가 오면; 도착하면 연락해.

“If” is not one Korean form

English if covers real conditions, future triggers, hypothetical imagination, instructions, requirements, and necessary conditions. Korean divides this work among several patterns.

• 시간이 있으면 연락해 주세요.
• 문제가 생기거든 전화해.
• 내가 부자라면 집을 살 텐데.
• 공부해야 합격한다.
• 도착하면 연락해.

These are all conditional in a broad sense, but they do not do the same discourse job.

면: ordinary condition or when

-(으)면 is the general workhorse.

• 시간이 있으면 만나요.
• 비가 오면 안 갈 거예요.
• 도착하면 연락해.
• 이 버튼을 누르면 화면이 바뀝니다.

It can mean if or when depending on context. 도착하면 연락해 usually means “when you arrive, contact me,” not a doubtful “if you arrive.” 면 is a safe first pattern for many conditions, but it is not the only one.

거든: conversational trigger and instruction

거든 often appears when the first clause sets a possible future trigger for the listener’s action:

• 문제가 생기거든 전화해.
• 시간이 나거든 한번 들러.
• 궁금하거든 물어보세요.
• 도착하거든 연락해 주세요.

It often feels conversational and instruction-like: if or when this happens, then do this. This article focuses on connective 거든, not the sentence-final explanatory 거든요.

다면: hypothetical or formal framing

다면 often marks a more hypothetical, imagined, or formally framed condition.

• 내가 부자라면 큰 집을 살 텐데.
• 다시 태어난다면 뭘 하고 싶어요?
• 이 주장이 사실이라면 문제가 큽니다.
• 시간이 허락된다면 참석하겠습니다.

It is common in essays, interviews, formal statements, and hypothetical reflection. It can feel more distant or framed than plain 면.

아/어야: necessary condition

아/어야 marks a condition that must be satisfied for the result.

• 공부해야 합격해요.
• 빨리 가야 늦지 않아요.
• 먹어야 힘이 나요.
• 신청해야 참여할 수 있어요.

This is closer to “only if,” “must do in order to,” or “have to... to...” than simple if.

Compare:

• 공부하면 합격할 수 있어요. = if you study, you can pass
• 공부해야 합격할 수 있어요. = you have to study to pass

려면 is also useful

-(으)려면 means “if you intend to” or “in order to.”

• 한국어를 잘하려면 많이 들어야 해요.
• 일찍 도착하려면 지금 출발해야 해요.
• 신청하려면 신분증이 필요해요.

It combines intention/purpose with condition and often pairs with 해야 하다.

A conditional decision routine

1. Is this an ordinary if/when condition? Use 면 as first guess.
2. Is it a conversational trigger for advice, instruction, or request? Consider 거든.
3. Is it hypothetical, imagined, or formally framed? Consider 다면.
4. Is it a necessary condition for the result? Use 아/어야.
5. Is it “if you want/intend to”? Consider 려면.
6. Does the main clause give advice, command, result, regret, or possibility?
7. Is the register spoken, formal, written, or reflective?

Technical-review guardrail: conditionals include main-clause expectations

면, 거든, 다면, 아/어야, and 려면 differ not only in condition type but also in what kind of main clause naturally follows: advice, instruction, regret, possibility, requirement, or hypothetical reflection. Sentence-final 거든요 is a different use from connective 거든 and should not be mixed into the same learner rule.

Mini practice: choose the condition type

Suggested functions:

1. Scenario cards: advice, warning, dream, instruction, rule, requirement.
2. Form selector: 면, 거든, 다면, 아/어야, 려면.
3. Likelihood slider: real, possible, hypothetical, required.
4. Main-clause compatibility: command, suggestion, regret, formal statement.
5. Rewrite comparison: shows nuance changes across forms.
6. English warning: prevents treating all forms as identical if.

Final rule

Do not use 면 for every English if. Decide whether the condition is ordinary, triggered, hypothetical, necessary, or tied to intention.