<Let's learn about "밥 먹자"

밥 먹자 : Let's dig in; Let's eat meal

[other expressions]

- 밥 먹자. (to younger people or your friends)

- 밥 먹게. (to younger people or your friends)

- 밥 먹어. (to younger people or your friends)

- 밥 먹어라. (to younger people or your friends)

- 밥 먹어요. (honourific by '-요')

- 밥 드세요. (more honourific by '-시')

- 밥 드셔요. (more honourific by '-시')

<to the elderly like your parent, grandpa, grandma>

- 진지 드세요. (more honourific by '-시')

- 진지 드셔요. (more honourific by '-시')

- 진지 드십시오. (more honourific by '-시')

[explanations]

* 밥 : meal (non-honourific word)

* 진지 : meal (honourific word to the elderly like your parent, grandpa, grandma)

* -을 : a particle makes 밥 objective after a word ends in a consonant

* -를 : a particle makes 진지 objective after a word ends in a vowel

* 먹다 : eat (non-honourific word)

* 들다 : eat (non-honourific word)

* 드시다 : an honourific form of 들다 to the elderly by '-시'

* 먹자 : 먹(the stem of 먹다) + -자(a non-honourific propositive or imperative verb ending suffix means "Let's ~")

* 먹게 : 먹(the stem of 먹다) + -게(the speaker’s wish; a non-honourific propositive or imperative verb ending suffix means "Let's ~")

* 먹어라 : 먹(the stem of 먹다) + -어라(a non-honourific propositive or imperative verb ending suffix) 

* 드세요 : 들(the stem of 들다; ㄹ erased before ㅅ) + -시(a suffix makes a verb more honourific) + -어(a propositive verb ending suffix) + -요(an honourific verb ending suffix)

* 드셔요 : 들(the stem of 들다; ㄹ erased before ㅅ) + -시(a suffix makes a verb more honourific) + -여(a propositive verb ending suffix) + -요(an honourific verb ending suffix)

* 드십시오 : 들(the stem of 들다; ㄹ erased before ㅅ) + -시(a suffix makes a verb more honourific) + -ㅂ시오(an honourific propositive verb ending suffix)

* a verb + -어 / -어라 / -게 : a non-honourific propositive verb ending suffix

* a verb + -어 + -요 : an honourific verb ending suffix

* a verb + -세요 / -셔요 / -십시오 : an honourific propositive verb ending suffix by '시' / '-요' / '-오'