-어서

V/Adj/이다,아니다 + 아/어서 1. This indicates a reason or cause. (because)

요즘 너무 추워서 감기에 걸렸어요.

I caught a cold because it's been too cold lately.

배불러서 밥을 남겼어요.

I left some food because I was full.

넘어져서 다리를 다쳤어요.

I hurt my leg because I fell down.

• For this meaning, You can’t use with imperative or suggesting ending pattern.

열이 나서 병원에 갈까요? X

배가 아파서 약을 먹으세요. X

V + 아/어서 2. This indicates the order of time. (and then) ‘-어서’ also means ‘and’ like ‘-고’. However, it shows a stronger connection between actions, as a natural sequence of events.

약국에 가서 약을 받았어요.

I went to the pharmacy and got medicine.

돈을 모아서 여행을 갈 거예요.

I'll save money and go on a trip.

친구를 만나서 영화를 봤어요.

I met a friend and watched a movie (together).

• -고 vs -어서

고	어서
토니 씨는 친구를 만나고 영화를 봤어요 Tony met a friend and he watched a movie. We don’t know whether he watched it with that friend or alone after parting ways.	토니 씨는 친구를 만나서 영화를 봤어요 Tony met a friend and he watched a movie with that friend. While -어서 has a similar meaning to -고 (and), it has the meaning of a chain effect where the two clauses' actions are related to each other.

• For ‘Noun + 이다/아니다’, you can also use “(이)라서/아니라서”.

여름이어서 더워요. = 여름이라서 더워요. Because it's summer, it's hot.

• Tense: always base form

추웠어서 감기에 걸렸어요 X → 추워서 O

춥겠어서 감기에 걸릴 거예요 X → 추워서 O