This pattern shows cause or reason.

- used with any verb
- the verb in the final tense is usually in the past tense
- if the action of the first clause is completed before the action of the main/final clause, then the verb it attaches to may be in the past tense
- also used to ask the reason behind a certain fact, event, or action. When this pattern is used in the present tense, it is usually answered with the grammar pattern -느라고
— however, if used in this manner but in the past tense, it's answered with the grammar pattern -더니
- 기에 and 길래 are mostly interchangeable but 기에 tends to be used for formal/written language whereas 길래 is used in spoken/colloquial usage

Examples:
모리는 많이 아프길래, 병원에 갔습니다./My head hurt very much , so I went to the hospital.
뭘 하길래 오지않아요?/What is he doing that he can't come?; 일하느라고, 아지 않아./He's working, so he can't come.
그 의자가 싸기에, 한 깨 샀어요./Because that chair was cheap, I bought one.