Because / So

This pattern connects two clauses to show a cause-and-effect relationship. The first clause, ending in -아/어서, gives the reason or cause for the action or state described in the second clause. It's equivalent to saying "because..." or "so..." in English.

Formation

For verbs/adjectives with a stem ending in ㅏ or ㅗ: Add -아서.

가다 (to go) → 가서

보다 (to see) → 봐서 (irregular contraction)

만나다 (to meet) → 만나서

For verbs/adjectives with a stem ending in other vowels: Add -어서.

먹다 (to eat) → 먹어서

읽다 (to read) → 읽어서

예쁘다 (to be pretty) → 예뻐서 (irregular contraction)

For 하다 verbs/adjectives: They become -해서.

피곤하다 (to be tired) → 피곤해서

For nouns: Add -(이)라서.

처음 (first time) → 처음이라서

학생 (student) → 학생이라서

Tense

The tense of the entire sentence is always indicated in the final verb of the second clause. The -아/어서 clause itself does not get conjugated for tense.

Correct: 배고파서 밥 먹었어요. (I was hungry, so I ate.)

Incorrect: 배고팠어서 밥 먹었어요.

배고파서 현기증 나. / 너무 비싸서 못 샀어. / 비가 와서 못 갔어요. / 처음이라서 긴장돼.

-아/어서 is a key component of many fixed, high-frequency expressions in Korean for greetings, apologies, and thanks. In these cases, the cause-and-effect logic is still there, but they function like set phrases.

Greetings: 만나서 반갑습니다. (Nice to meet you.)

Reason: We met. Result: I am pleased.

Apologies: 늦어서 미안해요. (Sorry I'm late.)

Reason: I am late. Result: I am sorry.

Gratitude: 도와줘서 고마워요. (Thank you for helping.)

Reason: You helped me. Result: I am thankful.

Memorizing these common phrases will help you sound more natural and use -아/어서 instinctively.