what the difference 먹어 and 식사 먹다 = to eat==== 먹어 = eat 식사 = meal 우리는 식사를 해야해요/ 우리는 밥을 먹어야해요 = we have to eat meal.

먹어= this is a command you say to someone to eat. It's like "eat!". You can only say this to someone younger than you or someone that is close because it is an impolite tone. Do not ever say this to an older person as it would be very rude. The impolite word for meal is "밥" (it also literally means rice). If you want to tell someone to eat a meal in an impolite way is 밥 먹어. 식사= this means "a meal". This is a POLITE form. Because this is a polite form for a meal, you cannot mix this with the impolite 먹어 and say 식사를 먹어. The polite form to ask someone to eat is 드세요. So you say "식사 드세요". Korean is complicated like that because the society heavily focuses on respect to elders. The polite/impolite thing will confuse you for a while. But you'll soon learn the pattern and be good at it :)

먹어 = do eat http://endic.naver.com/search.nhn?query=%EB%A8%B9%EC%96%B4&searchOption=entry_idiom 식사 = meal http://endic.naver.com/search.nhn?&searchOption=entry_idiom&isOnlyViewEE=N&query=%EC%8B%9D%EC%82%AC