-았어요/었어요: Korean Past Tense, Built From What You Know

Korean past tense is the one piece of beginner grammar that asks nothing new of you. If you can build -아요 / -어요, you already have it.

The rule is the rule you know

Take the stem, apply the same vowel test, and insert 았 or 었 before 어요.

ㅏ or ㅗ → 았어요
anything else → 었어요
하다 → 했어요

가다   →  가요    →  갔어요
좋다   →  좋아요  →  좋았어요
먹다   →  먹어요  →  먹었어요
공부하다 → 공부해요 → 공부했어요

가 + 았어요 merges to 갔어요, exactly as 가 + 아요 merged to 가요. The contraction behaves the same way at both tenses.

Every irregular carries over

This is the part worth stating plainly: you do not learn a second set of irregulars.

The stem change happens once, when you build the 해요 form. The past marker attaches to whatever came out of that.

So the practical advice is: get the present tense automatic, and the past costs you nothing.

With nouns

이다 follows its own consonant/vowel split, as always:

• 학생이었어요 — I was a student.
• 가수였어요 — I was a singer.

Same logic as 학생이에요 / 가수예요 in 이다, one layer deeper.

The mistake to avoid

The past marker does not go on connectors that refuse it.

어제 바빴어서 못 갔어요.   ❌
어제 바빠서 못 갔어요.     ✅

-아서 / -어서 never takes 았/었. The tense lives in the final verb — 못 갔어요 — and that is enough to place the whole sentence in the past.

-(으)니까 is the opposite: 바빴으니까 is completely normal. Each connector has its own rule, and this pair is the one that catches everyone.

Time words that refuse 에

어제에 갔어요.   ❌
어제 갔어요.     ✅

어제, 오늘, 내일, 지금, 매일 take no particle. Other time expressions do — 3시에, 월요일에, 작년에. There is no rule to derive; the list is short enough to memorise.

Two past markers

You will eventually meet -았었/-었었:

서울에 살았었어요 — I used to live in Seoul. (but not any more)

The doubled marker implies the situation has since changed. It is a real distinction, but not one you need while you are still making the basic past automatic.

A sentence you can build now

어제 친구를 만났어요. 같이 밥을 먹었어요.
I met a friend yesterday. We ate together.

Two past-tense sentences, built entirely from the present tense you already had.