The difference between 아서/어서 and (으)니까 ?

[isaacristich]

아서 / 어서 and (으)니까?

I'm having a bit of trouble figuring out the difference between these two. As I understand they both basically are used for contrasting subjects, and mean "since, so, because".

Any insight you can provide? Post it!

[cheri]

아서 / 어서 and (으)니까?

I'm having a bit of trouble figuring out the difference between these two. As I understand they both basically are used for contrasting subjects, and mean "since, so, because".

Any insight you can provide? Post it!

I think one of the main grammatical differences between the two is that you can't use the ~어서/아서 pattern when the second clause is a command or suggestion (i.e. imperative form). For example:

날씨가 추우니까 감기 조심하세요. (o)
날씨가 추워서 감기 조심하세요. (x)

피곤하니까 쉬자. (o)
피곤해서 쉬자. (x)

살찌니까 조금만 드세요. (o)
살쪄서 조금만 드세요. (x)

이것은 비싸니까 다른 것을 주세요. (o)
이것은 비싸서 다른 것을 주세요. (x)

So basically if the sentence ends with -(으)ㅂ시다, -(으)세요, -(으)십시오, etc. you will want to use the -(으)니까 form, not the -어서/아서 form.

Also, I'm not sure if this is entirely true or not (I often get different answers) so take this with a grain of salt, but this was the rule I got from someone (when you're not ending the sentence with a command/suggestion of course): 어서/아서 tends to be used when you're talking about your own feelings/thoughts while (으)니까 tends to be used when talking about something everyone can relate to. I'm also not really familiar with the nuances between the two when used in a statement.

앞으로는 3개월 밖에 안 남았으니까 열심히 공부하겠습니다.
vs. 앞으로는 3개월 밖에 안 남아서 열심히 공부하겠습니다.

I think I wrote some notes on this before... will try to look for it. ^^