A2
고 and 아/어서 — joining actions
How the Korean verb endings 고 and 아/어서 join clauses, and the movement verbs that force the choice.
Korean joins two actions by changing the first verb’s ending, not by adding a word between them. Only the final verb carries tense and politeness.
고 — and, in sequence
밥을 먹고 학교에 갔어요.
Babeul meokgo hakgyoe gasseoyo.
I ate and went to school.
손을 씻고 밥을 먹어요.
Soneul ssitgo babeul meogeoyo.
I wash my hands and eat.
Two actions, one after the other, otherwise unconnected. 갔어요 alone carries the past for both.
아/어서 — and so, carried through
학교에 가서 친구를 만났어요.
Hakgyoe gaseo chingureul mannasseoyo.
I went to school and met a friend there.
The difference is real. 가고 만났어요 would be two separate events — went somewhere, met someone somewhere. 가서 만났어요 says the meeting happened at the place you went to. The first action sets up the second.
앉아서 기다리세요.
Anjaseo gidariseyo.
Please sit and wait.
With movement verbs, 서 is required
시장에 가고 과일을 샀어요.
시장에 가서 과일을 샀어요.
Going somewhere and then doing something there always takes 서. 가고 would mean you went to the market and, separately, bought fruit somewhere else.
Neither takes a tense
The first verb stays in its bare form regardless of when it happened.
먹었고 갔어요.
먹고 갔어요.
The past lives in the final verb only. 먹었고 is possible in careful writing when the two events are genuinely separate, but 먹고 is what is said.