Grammar
-(ㄴ/는)다면
Meaning
Intermediate-(n/neun)damyeon
Marks a condition the speaker is only supposing — 'if it should be that ~', 'supposing that ~'. Where -(으)면 states a condition plainly, -(ㄴ/는)다면 holds the case at arm's length: it is put forward as one possibility, with nothing said about whether it is expected. That is why forecasts end in it. 특사가 이뤄지지 않는다면 … 될 전망입니다 does not say the year will end without a pardon; it says what would follow if it did.
Form
Built on the plain declarative -(ㄴ/는)다 plus -면. A verb stem takes -ㄴ다면 after a vowel (오다 → 온다면) and -는다면 after a consonant (먹다 → 먹는다면), and a ㄹ-final stem drops the ㄹ (살다 → 산다면); a negated verb goes through 않다, giving -지 않는다면. Adjectives add -다면 with no ㄴ/는 (좋다 → 좋다면), and 이다 becomes -(이)라면 (학생이라면), never 학생이다면. The past is -았/었다면. 만약 or 만일 often stands at the head of the clause as a signal that a supposition is coming.
Examples
비가 온다면 행사는 미뤄집니다.
If it should rain, the event will be postponed.
Common mistakes & nuance
-(ㄴ/는)다면 does not fit a condition that is expected to hold, or one that holds as a rule. 봄이 오면 꽃이 핍니다 is a general truth and stays with -(으)면; 봄이 온다면 would turn the arrival of spring into an open question. Two further things to know. With the past tense, -았/었다면 usually reads as counterfactual and pairs with -았/었을 것이다 ('if it had ~, it would have ~'). And the same string can be a contraction of quoted -(ㄴ/는)다고 하면, 'if someone says that ~', which is worth checking when the clause is reporting what a source claimed.
Similar grammar
- -(으)면
-(으)면 is the general conditional and covers everything from a real condition to a habit to a plain 'when' (한복을 입으면 입장료가 무료입니다). -(ㄴ/는)다면 is the marked choice and narrows to supposition, so it cannot take over those habitual and generic uses. Reaching for it where -(으)면 would do adds a shade of doubt the sentence may not have meant.
- -(으)ㄹ 경우
Both set up a case that may or may not arise, but -(으)ㄹ 경우 files it as a case ('in the event that ~') and stays neutral about how likely it is, which is what suits rules and manuals listing what to do in each situation. -(ㄴ/는)다면 keeps the speaker in the sentence, supposing the case rather than tabulating it.