- basic present tense

• ~아요 = verb stem’s last vowel is ㅏ or ㅗ (ex. 가요, 봐요, 잡아요, 팔아요, 놀아요)
• ~어요 = verb stem's last vowel is NOT ㅏ or ㅗ (ex. 먹어요, 보여요, 멋있어요)
• ~여요 = verb stem 하 (ex. 하여요, which became 해요)
• (!) there are exceptions: 쓰다 is 써요, 기다리다 is 기다려요, 이상하다 is 이상해요, 멋있다 is

-past tense

• ~았어요 = verb stem's last vowel is ㅗ or ㅏ (ex. 샀어요, 왔어요, 잡았어요, 팔았어요, 놀았어요)
• ~었어요 = verb stem's last vowel is NOT ㅗ or ㅏ (ex. 적었어요, 먹었어요, 멋있었어요)
• ~였어요 = verb stem 하 (ex. 했어요)
• (!) there are exceptions: 쓰다 is 썼어요, 기다리다 is 기다렸어요, 이상하다 is 이상했어요