Putting your reason on the table: -(으)니까

Where the picture shows up in -(으)니까

1. 1

   the reason you hand over

   비 오니까 우산 가져가세요.

   bi o-ni-kka u-san ga-jyeo-ga-se-yo

   It's raining, so take an umbrella.

   A command cannot follow -어서, but it can follow -(으)니까.

2. 2

   grounds for doing it together

   시간 없으니까 택시 탑시다.

   si-gan eop-seu-ni-kka taek-si tap-si-da

   We're out of time, so let's take a taxi.

3. 3

   what you found on arriving

   집에 가 보니까 아무도 없었어요.

   ji-be ga bo-ni-kka a-mu-do eop-seo-sseo-yo

   I went home and found nobody there.

   It also marks something you discovered only after doing the first action.

4. 4

   the card under your claim

   제가 먼저 왔으니까 제가 낼게요.

   je-ga meon-jeo wa-sseu-ni-kka je-ga nael-ge-yo

   I got here first, so I'll pay.

5. 5

   the reason to put it off

   바쁘니까 나중에 얘기해요.

   ba-ppeu-ni-kka na-jung-e yae-gi-hae-yo

   I'm busy, so let's talk later.

   Don't use it for apologies or greetings. 늦어서 죄송합니다 is right; 늦으니까 죄송합니다 sounds broken.