Just a question about the past tense

[nilfisq]

Hello all!
I am still a(n enthousiastic) beginner and just completed the Beginner S1 lessons. In lesson 31 the past tense is introduced and in the accompanying PDF I find the following example

past tense (intimate politeness level): 바빠서 (I was busy)
dictionary form: 바쁘다

since the past tense infix is -었, -았 or 였 (all with ㅆ) I would expect this form to be:
바빴어

I consulted the Korean Grammar for International Learners and on p.192 I found a similar form for the verb 예쁘다, past tense 예뻤어요, which seems to confirm my presumption about the past tense of 바쁘다.

Looking forward to hear more about this from experienced KC101 fanatics

[Chris1]

바빴어 is correct. I don't know the context of which you saw 바빠서, but it is using a connective sentence structure (서) to possibly show cause and effect with a second clause. Since the ~서 form does not have a tense (i.e. you can't say 바빴어서), it is always 바빠서 with the connecting clause showing tense.

I hope this makes sense!

[nilfisq]

Thank you Chris, that makes perfectly sense: the verb form 바빠서 is indeed part of a longer sentence containing cause and effect.