그든요 is a wrong form of 거든요. I recommend you to use 거든요 instead of 그든요. 그든요 sounds childish. Quoted from http://www.learnkoreanlp.com/2012/12/because-im.html Because I'm - ~거든요 거든요 is used as a statement in which you give reasons / explanations for what you do or did. 하거든요 = Because (I) do 거든요 is a polite spoken form 거든 is a informal spoken form (however, if 거든 is used in the middle of a sentence (i.e. as a conjunction, linking two sentences), it means 'if') For example, 벌써 왔어? = You came (back) already? 줄이 너무 길었거든. 그래서 그냥 왔어 = Because the queue was too long. So I just came (back). 줄이 너무 길거든, 그냥 와 = If the queue is too long, just come (back). Take 다 off verbs/adjectives and add 거든요. 왔거든요 = Because (he) came 많았거든요 = Because (there) were many 배고팠거든요 = Because (I) was hungry 빠르거든요 = Because (it's) fast 맛있거든요 = Because (it's) delicious E.g. 아침 안 먹어요? = Don't you have breakfast? 네, 어제 저녁을 너무 많이 먹었거든요. = Yeah no, (because) I ate too much for dinner last night. Example sentences 새 노트북 샀네요? = (Hey,) you bought a new laptop 네, 예전 노트북은 너무 느렸거든요. 그래서 새 노트북 샀어요 = Yeah, (because) the laptop I had before was too slow. So I bought a new laptop. 여기 레스토랑 음식이 진짜 맛있거든. 여기서 먹을래? = (Because) this restaurant's food is really delicious. Shall we eat here? 그래, 좋지. = Yeah, I'd like to.