-아서/어서

RuleVerb/adjective stem + -aseo/eoseo: gives a reason ("because") or a preceding action ("and then"). Vowel harmony picks -aseo or -eoseo.

Curiosity

In "I was hungry, so I ate," the "-aseo" links a reason. How does it differ from -go?

Intuition

-aseo/eoseo binds the two halves by cause or tight sequence. Where -go just lists, -aseo/eoseo makes the first clause the ground for the second ("so / and then"). It reads naturally when both halves share one subject.

Visualization

gada (dictionary) → ga (stem) → gaseo. ga + aseo contracts to gaseo.

가다gadadictionary form

Essence

If the stem vowel is a/o use -aseo; otherwise -eoseo (meogeoseo); hada becomes -haeseo. It shows reason or time sequence, and the first clause does not take a tense marker (-eot-). A command or suggestion rarely follows the reason -aseo/eoseo — use -(eu)nikka for that.

Examples

배가 고파서 밥을 먹었어요.

I was hungry, so I ate.

도서관에 가서 공부했어요.

I went to the library and studied (there).

늦어서 죄송합니다.

I am sorry for being late.

Mini-quiz

Attach the reason -aseo/eoseo to "meokda" (to eat). (stem vowel eo)