Past Tense: 았/었어요
Turn present tense sentences into past tense using 았/었어요.
Past tense in Korean is formed by inserting -았/었- between the verb stem and the polite ending -어요. The vowel choice follows the same harmony rule as the present: ㅏ/ㅗ stems take -았어요, everything else takes -었어요. 하다 verbs become 했어요.
Examples: 먹다 (eat) → 먹었어요 (ate), 가다 (go) → 갔어요 (went — the ㅏ of 가 fuses with the 았 of -았어요 to produce 갔), 마시다 (drink) → 마셨어요 (drank), 공부하다 (study) → 공부했어요 (studied). The past tense in Korean is just one tense — there is no distinction between 'I ate' / 'I have eaten' / 'I was eating' the way English makes. Context tells you which English equivalent fits. This makes Korean past tense easier than English past tense for once.
Past Tense: 았/었어요
Same vowel rule as present: if stem vowel is ㅏ/ㅗ → 았어요, otherwise → 었어요, 하다 → 했어요. Just replace 아요/어요 with 았어요/었어요.
Time Words for Past Tense
Common time words: 어제 (yesterday), 지난주 (last week), 지난달 (last month), 작년 (last year), 아까 (a while ago), 방금 (just now).