Let's learn about "추우니까 문 닫아"

추우니까 문 닫아 : It's (so) cold, so please close the door

[other expressions]

<to younger people or friends>

- 추우니까 문 닫아.

- 추우니까 문 닫아라.

<to your family; but it's better not to use this because this is rude>

- 추우니까 문 닫아요. (honourific by ‘요’)

- 추우니까 문 닫으세요. (honourific by ‘요’)

- 추우니까 문 닫으셔요. (honourific by ‘요’)

- 추우니까 문 닫으시지요. (honourific by ‘요’)

- 추우니까 문 닫으시죠. (honourific by ‘요’; -죠 is a short form of -지요)

- 추우니까 문 닫으십시오. (more honourific by ‘시’)

[explanations]

* 추운 : cold; algid

* 춥다 : [ㅂ 불규칙] be cold; be algid

* 추워 : 춥(the stem of 춥다; ㅂ changed into 우) + -어(a non-honourific descriptive verb ending suffix)

* ㅂ 불규칙 : the ㅂ of 춥다 is not 'B' sound but 'V' sound and V consists of ㅂ + 옛이응  ‘ㆁ’. these days  V sound changed into '우' for easy pronunciation

* See : https://m.blog.naver.com/nurisejong/221050681781

* 추우니까 : 춥(the stem of 춥다; ㅂ changed into 우 before 니) + -니까(because of)

* -니까 : an emphatic word of -니; (1) [강조] thus; so; I say; I tell you (2) 이유·원인] now that; since; because; due to

- 괜찮다니까 : You needn't do it, I tell you!

- 싫다니까 : I tell you I don't like it

- 네가 그렇게 말하니까 : now that you say so ‥.

- 그는 개를 무서워하니까 : 검둥이를 보자 도망쳐 버렸다 Being afraid of dogs, he ran away at the sight of Blackie

- 식사 준비가 다 된 모양이니까 식당으로 가십시다 : As the meal seems to be all ready, let's go along to the dining room

- 오늘은 토요일이니까 일찍 돌아오겠다 : I'll be back home earlier than usual because it is Saturday today

* 닫다 :  close (the door)

* 닫아 : 닫(the stem of 닫다) + -아(a non-honourific propositive verb ending suffix means "please ~")

* 닫아라 : 닫(the stem of 닫다) + -아라(a non-honourific propositive verb ending suffix means "do ~")

* 닫으세요 : 닫(the stem of 닫다) + -으시(s suffix makes a verb more honourific) + -어(a propositive verb ending suffix means "do ~") + -요(an honourific verb ending suffix)

* 닫으셔요 : 닫(the stem of 닫다) + -으시(s suffix makes a verb more honourific) + -여(a propositive verb ending suffix means "do ~") + -요(an honourific verb ending suffix)

* 닫으십시오 : 닫(the stem of 닫다)  + -으시(s suffix makes a verb more honourific) + -ㅂ시오(an  honourific propositive verb ending suffix means "do ~")

* a verb + -아 / -아라 : a non-honourific propositive verb ending suffix means "please ~"

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

* a verb + -으세요 / -으셔요 / -으십시오 / -으시지요 / -으시죠 : an  honourific propositive verb ending suffix means "do ~" by '-시' / '-오' / '-요'