Indicating a Reason with '서'

01

Conjugation Rules

• If the last vowel of the stem is ㅏ (a) or ㅗ (o), add 아서 (a·sŏa·seoa·sŏa·se).
• If the last vowel is anything else, add 어서 (ŏ·sŏeo·seoŏ·sŏe·se).
• If the verb ends in 하다 (ha·daha·daha·daha·ta), it becomes 해서 (hæ·sŏhae·seohae·sŏhay·se).

• 배가 고파서 밥을 먹어요.

  pæ·ga go·pʰa·sŏ bab·ŭl mŏg·ŏ·yo.bae·ga go·pa·seo bab·eul meog·eo·yo.pae·ga go·p'a·sŏ bab·ŭl mŏg·ŏ·yo.pay·ka ko·pha·se pab·ul meg·e·yo.

  I am hungry, so I am eating rice.

• 비가 와서 집에 있어요.

  pi·ga wa·sŏ jib·e iss·ŏ·yo.bi·ga wa·seo jib·e iss·eo·yo.pi·ga wa·sŏ jib·e iss·ŏ·yo.pi·ka wa·se cib·ey iss·e·yo.

  It is raining, so I am at home.

• 피곤해서 자고 싶어요.

  pʰi·gon·hæ·sŏ ja·go sip·ŏ·yo.pi·gon·hae·seo ja·go sip·eo·yo.p'i·gon·hae·sŏ ja·go sip·ŏ·yo.phi·kon·hay·se ca·ko sip·e·yo.

  I am tired, so I want to sleep.

02

Tense Restrictions

As in every use of 서 (sŏseosŏse) (see Connective Suffix '서'), no past marker such as 았 (at) or 었 (ŏteotŏtet) goes before it; only the final verb carries the tense. A reason that lies in the past keeps the plain form too.

• 어제 아파서 병원에 갔어요.

  ŏ·je a·pʰa·sŏ byŏng·won·e gass·ŏ·yo.eo·je a·pa·seo byeong·won·e gass·eo·yo.ŏ·je a·p'a·sŏ byŏng·wŏn·e gass·ŏ·yo.e·cey a·pha·se pyeng·wen·ey kass·e·yo.

  I was sick yesterday, so I went to the hospital.

• 돈이 없어서 못 샀어요.

  ton·i ŏps·ŏ·sŏ mot sass·ŏ·yo.don·i eops·eo·seo mot sass·eo·yo.ton·i ŏps·ŏ·sŏ mot sass·ŏ·yo.ton·i eps·e·se mot sass·e·yo.

  I didn't have money, so I couldn't buy it.

03

Social Expressions: Thanks and Apologies

서 (sŏseosŏse) is the standard way to give a reason for emotions, specifically when greeting, thanking, or apologizing. In these fixed expressions, you cannot use other causal endings like 니까 (ni·kkani·ggani·kkani·kka).

• 만나서 반가워요.

  man·na·sŏ ban·ga·wo·yo.man·na·seo ban·ga·wo·yo.man·na·sŏ ban·ga·wŏ·yo.man·na·se pan·ka·we·yo.

  Nice to meet you. (Lit: Because we met, I am glad.)

• 늦어서 죄송합니다.

  nŭj·ŏ·sŏ jwæ·song·ham·ni·da.neuj·eo·seo jwae·song·ham·ni·da.nŭj·ŏ·sŏ jwae·song·ham·ni·da.nuj·e·se cway·song·ham·ni·ta.

  I am sorry for being late. (Lit: Because I am late, I am sorry.)

• 도와줘서 고마워요.

  to·wa·jwo·sŏ go·ma·wo·yo.do·wa·jwo·seo go·ma·wo·yo.to·wa·jwŏ·sŏ go·ma·wŏ·yo.to·wa·cwe·se ko·ma·we·yo.

  Thank you for helping.

04

Restrictions on Commands and Suggestions

You cannot use 서 (sŏseosŏse) when the second clause is a command ("Do this"), a suggestion ("Let's do this"), or a proposal. If you want to give a reason for a command or suggestion, you must use the ending (으)니까 ((ŭ)ni·kka(eu)ni·gga(ŭ)ni·kka(u)ni·kka) instead.

Incorrect: 추워서 코트를 입으세요. (chʰu·wo·sŏ kʰo·tʰŭ·rŭl ib·ŭ·se·yo.chu·wo·seo ko·teu·reul ib·eu·se·yo.ch'u·wŏ·sŏ k'o·t'ŭ·rŭl ib·ŭ·se·yo.chu·we·se kho·thu·lul ib·u·sey·yo.) (It's cold, so please wear a coat.)

Correct: Use (으)니까 ((ŭ)ni·kka(eu)ni·gga(ŭ)ni·kka(u)ni·kka) for this situation.

• 추우니까 코트를 입으세요.

  chʰu·u·ni·kka kʰo·tʰŭ·rŭl ib·ŭ·se·yo.chu·u·ni·gga ko·teu·reul ib·eu·se·yo.ch'u·u·ni·kka k'o·t'ŭ·rŭl ib·ŭ·se·yo.chu·u·ni·kka kho·thu·lul ib·u·sey·yo.

  It is cold, so please wear a coat.

• 시간이 없으니까 빨리 가요.

  si·gan·i ŏps·ŭ·ni·kka ppal·li ga·yo.si·gan·i eops·eu·ni·gga bbal·li ga·yo.si·gan·i ŏps·ŭ·ni·kka ppal·li ga·yo.si·kan·i eps·u·ni·kka ppal·li ka·yo.

  We don't have time, so let's go quickly.

05

Summary of Differences

While both 서 (sŏseosŏse) and (으)니까 ((ŭ)ni·kka(eu)ni·gga(ŭ)ni·kka(u)ni·kka) translate to "because/so", remember these distinctions:

• 서 (sŏseosŏse) states a natural cause and its effect as plain fact. It is the form for thanks and apologies, takes no past marker, and cannot be followed by a command or a suggestion.
• (으)니까 ((ŭ)ni·kka(eu)ni·gga(ŭ)ni·kka(u)ni·kka) gives the speaker's own reason, often one the listener should take into account. It is the form for commands and suggestions, and it can take the past marker: 비가 왔으니까 (pi·ga wass·ŭ·ni·kkabi·ga wass·eu·ni·ggapi·ga wass·ŭ·ni·kkapi·ka wass·u·ni·kka) - since it rained.