Basic words of verb are made up of verb+다
It can be changed as verb+어 for casual way
ex) 먹다 -> 먹어
It can be changed as verb+어/아요 for polite way
ex) 먹다 -> 먹어요
Changing verbs for past tense verb+었/았다
ex)먹다 -> 먹었어(casual) 먹었어요(polite)
Changing verbs for future tense verb+ㄹ/일/를/을 거야/것이다
ex)먹다 -> 먹을 거야(casual) 먹을 거예요(polite)
가아요 -> 가요 because ㄱ + (ㅏ = 아 ) same sound