This is the 14086th most frequent Korean word.
먹여야
"먹여야" means "must feed" or "have to feed."
Here, '먹여야' is used to express the necessity ('you have to') of feeding someone ('먹이다' is the causative form of '먹다').
아기가 배고파서 엄마가 아기에게 밥을 먹여야 합니다.
The baby is hungry, so the mother needs to feed the baby.
In this sentence, '먹여야' is employed to denote the requisite action of feeding ('먹이다').
동물을 키우는 사람은 매일 먹이를 먹여야 해요.
People raising animals need to feed them daily.
Here, '먹여야' indicates the obligation to carry out the action of feeding someone ('먹이다').