-(으)니까 vs -아/어서: Imperatives without snark

When it’s the right choice

Use -(으)니까-(eu)nikka when your reason is meant to justify what comes next—especially if what comes next is an instruction or suggestion.

A small real-life trap: I once texted a teammate a reason + request with -(으)니까-(eu)nikka, and it read like “because you messed up…” even though I only meant “given the situation.” The grammar was fine; the vibe wasn’t.

Minimal pairs (vs -아/어서)

Here are common “wrong → right” fixes when you’re trying to command/suggest (the “imperative test”):

1. *늦어서 서둘러.*neujeoseo seodulreo. → 늦으니까 서둘러.neujeunikka seodulreo. — You’re late, so hurry up.
2. *바빠서 먼저 가.*bappaseo meonjeo ga. → 바쁘니까 먼저 가.bappeunikka meonjeo ga. — You’re busy, so go first.
3. *비가 와서 우산 가져가.*biga waseo usan gajyeoga. → 비가 오니까 우산 가져가.biga onikka usan gajyeoga. — It’s raining, so bring an umbrella.
4. *시간이 없어서 빨리 해.*sigani eopseoseo ppalri hae. → 시간이 없으니까 빨리 해.sigani eopseunikka ppalri hae. — We don’t have time, so do it quickly.
5. *배고파서 밥 먹자.*baegopaseo bap meokja. → 배고프니까 밥 먹자.baegopeunikka bap meokja. — I’m hungry, so let’s eat.

Examples

• 지금 비가 오니까 우산 가져가.jigeum biga onikka usan gajyeoga. — It’s raining now, so bring an umbrella.
• 회의가 곧 시작하니까 휴대폰은 무음으로 해 줘.hoeuiga got sijakhanikka hyudaeponeun mueumeuro hae jwo. — The meeting’s about to start, so please put your phone on silent.
• 내일 일찍 일어나야 하니까 오늘은 먼저 잘게.naeil iljjik ireonaya hanikka oneureun meonjeo jalge. — I have to wake up early tomorrow, so I’ll go to sleep first.
• 네가 그렇게 말하니까 좀 서운했어.nega geureotge malhanikka jom seounhaesseo. — When you say it like that, it stings a bit. (This can feel direct, so mind the mood.)

When it’s the right choice

Use -아/어서-a/eoseo when you’re linking a cause to a result (facts → outcome), or when you’re giving an explanation/apology in a neutral, report-like tone.

In workplace Korean, -아/어서-a/eoseo is often the safer default for “here’s what happened” and “sorry” lines:

• 늦어서 죄송합니다.neujeoseo joesonghapnida. — Sorry I’m late.

One key constraint to remember: -아/어서-a/eoseo usually does not directly justify a command/request (like “so please do X”). If you need an explanation + a request, either use -(으)니까-(eu)nikka in one sentence, or split it into two sentences (explanation first, request second).

Minimal pairs (vs -(으)니까)

Here are pairs where -아/어서-a/eoseo is the more natural choice (especially for apologies and neutral reporting). In some cases both forms are possible; the difference is mostly tone.

6. 늦으니까 죄송합니다.neujeunikka joesonghapnida. → 늦어서 죄송합니다.neujeoseo joesonghapnida. — Apologies strongly prefer -아/어서-a/eoseo.
7. 제가 확인을 못 했으니까 죄송합니다.jega hwagineul mot haesseunikka joesonghapnida. → 제가 확인을 못 해서 죄송합니다.jega hwagineul mot haeseo joesonghapnida. — Same: -아/어서-a/eoseo sounds standard and professional.
8. 길이 막히니까 좀 늦었어요.giri makhinikka jom neujeosseoyo. → 길이 막혀서 좀 늦었어요.giri makhyeoseo jom neujeosseoyo. — Both OK; -아/어서-a/eoseo sounds more matter-of-fact.
9. 자료가 없으니까 진행이 안 됐어요.jaryoga eopseunikka jinhaei an dwaesseoyo. → 자료가 없어서 진행이 안 됐어요.jaryoga eopseoseo jinhaei an dwaesseoyo. — Both OK; -아/어서-a/eoseo reads like a plain cause→result report.
10. 피곤하니까 먼저 갈게요.pigonhanikka meonjeo galgeyo. → 피곤해서 먼저 갈게요.pigonhaeseo meonjeo galgeyo. — Both OK; -아/어서-a/eoseo feels less like you’re “making a case.”

Examples

• 길이 막혀서 10분 정도 늦을 것 같아요.giri makhyeoseo 10bun jeongdo neujeul geot gatayo. — Traffic is bad, so I think I’ll be about 10 minutes late.
• 정리가 안 돼서 다시 보내 드릴게요.jeongriga an dwaeseo dasi bonae deurilgeyo. — It wasn’t organized, so I’ll send it again.
• 소리가 커서 집중이 잘 안 돼요.soriga keoseo jipjui jal an dwaeyo. — The noise is loud, so I can’t focus well.
• 제가 착각해서 잘못 보냈어요.jega chakgakhaeseo jalmot bonaesseoyo. — I misunderstood and sent it wrong.