Grammar
-(으)ㄴ/는 데다
Meaning
Advanced-(eu)n/neun deda
A formal additive connective: the second clause is added to the first, and the two together produce the result. Attach 는 데다 to a present-tense verb and -(으)ㄴ 데다 to an adjective or a past-tense verb (늘어난 데다). It is stronger than a plain 그리고 because it signals that the causes are piling up; 가 is often added (데다가). Note that 데 here is the bound noun 'point/case', so it is written as a separate word.
Form
데 is a noun, so the clause in front takes a modifier ending: 는 데다 on a verb in the present (오르다 → 오르는 데다, 오다 → 오는 데다), and -(으)ㄴ 데다 on a completed action (오르다 → 오른 데다, 늘어나다 → 늘어난 데다) or on a descriptive verb (비싸다 → 비싼 데다, 좁다 → 좁은 데다, 많다 → 많은 데다). ㄹ-final stems drop the ㄹ before ㄴ: 멀다 → 먼 데다. 가 is very often added with no change of meaning (데다가), and the second clause usually carries 까지 or 도 to underline the piling-up: 수요까지 늘어, 시간도 부족해서. Both clauses have to push in the same direction — for an opposition you need -(으)ㄴ/는 반면 instead.
Examples
값이 오른 데다 수요까지 늘어 거래가 활발합니다.
On top of prices going up, demand has grown as well, so trading is brisk.
이 집은 값이 비싼 데다 역에서도 멉니다.
This house is expensive, and on top of that it is far from the station.
비가 오는 데다 바람까지 불어서 밖에 나가지 않았습니다.
It was raining, and on top of that the wind was blowing, so I did not go outside.
일이 많은 데다 시간도 부족해서 도와주지 못했습니다.
I had a lot of work, and on top of that I was short of time, so I could not help.
Common mistakes & nuance
-(으)ㄴ/는 데다 only stacks things that pull the same way. If the second clause contradicts the first, this is the wrong form and the sentence will read oddly. Watch the space too: 데 is a bound noun, so 오른 데다 is written apart — running it together as 오른데다 makes it look like the ending -(으)ㄴ데.
Similar grammar
- -뿐만 아니라
-뿐만 아니라 simply adds a second item to the first ('not only A but also B'). -(으)ㄴ/는 데다 adds a second situation that combines with the first to bring about the result, so it usually leads into a consequence.
- -고
-고 is the neutral 'and' and merely joins two clauses in order. -(으)ㄴ/는 데다 makes a point of the accumulation — it tells the reader that the reasons are adding up, which -고 never does.