Past Tense · -았어요/었어요

2. How it works

2.1 The basic formula

Take the dictionary form, remove 다 to get the stem, and add the past ending. Nothing else in the sentence changes. The same ending works for verbs and for adjectives.

Stem (last vowel ㅏ, ㅗ)  + 았어요  →  past
Stem (any other vowel)   + 었어요  →  past
하다                      →  했어요

The ending 아요/어요 is the present polite form you already know. The past form simply puts 았 or 었 in front of 어요. So 먹어요 (I eat) becomes 먹었어요 (I ate).

2.2 Choosing -았어요 or -었어요

Look at the last vowel in the stem. This works like the choice between 아요 and 어요 in the present. If the vowel is ㅏ or ㅗ, use 았. For every other vowel, use 었.

Only the last vowel counts. For a longer stem such as 재미있다, look at the last syllable 있, which has ㅣ, so the past is 재미있었어요.

2.3 The verb 하다

하다 does not follow the vowel rule. It always becomes 했어요, and so does every verb that ends in 하다. Think of it as one fixed piece to memorise.

하다       →  했어요         hae-sseo-yo
공부하다   →  공부했어요     gong-bu-hae-sseo-yo
일하다     →  일했어요       il-hae-sseo-yo

Do not say 하었어요. There are many 하다 verbs in Korean, such as 운동하다 and 전화하다, and all of them end in 했어요 in the past.

2.4 Stems that end in a vowel

When the stem already ends in a vowel, the stem and 았/었 usually join into one syllable. You will hear and read the joined form almost all the time. Learn the common ones as whole words.

For 마시다, the joined form 마셨어요 is the usual one. The long form 마시었어요 is also grammatical, but people rarely say it. A stem that ends in ㅏ or ㅓ just keeps one vowel, so 가 + 았 is 갔 and 서 + 었 is 섰.

2.5 Common verbs in the past

Here are eleven useful verbs. Notice that every form ends in -ㅆ어요, which is a good clue that a sentence is in the past.

2.6 이다 and time words

The past of 이다 depends on the noun before it. After a consonant use 이었어요. After a vowel use 였어요. For the negative, 아니다 becomes 아니었어요.

학생 + 이었어요  →  학생이었어요   hak-saeng-i-eo-sseo-yo   was a student
의사 + 였어요    →  의사였어요     ui-sa-yeo-sseo-yo         was a doctor

Time words help the listener know it is the past. Common ones are 어제 (yesterday), 지난주 (last week), 작년 (last year) and 아까 (a little while ago). A question uses the same form with a rising tone, so 먹었어요? means Did you eat?