Let's learn about "식은 죽 먹기"

그건 식은 죽 먹기야! : It's a piece of cake! (Cest du gâteau!)

[other expressions]

- 그건 식은 죽 먹기다. (to younger people or friends)

- 그건 식은 죽 먹기야. (to younger people or friends)

- 그건 식은 죽 먹기예요. (honourific by '-요')

- 그건 식은 죽 먹기입니다! (honourific by '-요')

[explanations]

* 그건 : a short form of 그것은

* 그것 : it; that

* -은 : a particle makes 그것 dubjective after a word ends in a consonant

*  식다 : (1) [=차게 되다] cool down; get cold (2) [=줄거나 가라앉다] abate; subside; br dampened (3) be chilled

* 식은 : 식(the stem of 식다) + -은(a suffix makes a verb past pefect and attributive)

* 죽 : soup

* 먹다 : eat

* 먹기 : 먹(the stem of 먹다) + -기(a sufifx makes a verb a noun)

* 이다 : be

* if a word ends in a vowel, "이다" contracted into "다"

- 먹기이다 --> 먹기다

- 먹기이야 --> 먹기야

- 먹기이에요 --> 먹기예요

* 먹기입니다 : 먹기+ 이(the stem of 이다) + -ㅂ니다(an honourific descriptive verb ending suffix by '-ㅂ')

* a noun + -이다 / -이야 : a non-honourific descriptive form of 이다

* a noun + -입니다 : an honourific descriptive form of 이다 suffix by '스' / '-ㅂ'