biga geuchimyeon chukjega sijakdwaeyo.

subject particle

Breakdown of biga geuchimyeon chukjega sijakdwaeyo.

• 비: rain
• 축제: festival
• ~면: if/when

Questions & Answers about biga geuchimyeon chukjega sijakdwaeyo.

What does -면 mean here, and is it if or when?

-면 is a conditional/time marker meaning if/when.
In real-life situations that are expected to happen (like rain stopping), -면 often translates naturally as when: When the rain stops, the festival starts.
It can also be if in more hypothetical contexts, but this sentence sounds like a practical schedule/plan.

How is 그치면 formed from the dictionary form 그치다?

Dictionary form: 그치다 (to stop; to cease—typically about rain, wind, etc.).
Stem: 그치-
Add -면 → 그치면 = if/when it stops.

Why is it 비가 (subject marker -가) instead of 비를 (object marker -를)?

Because 비 (rain) is the thing doing the action 그치다 (stopping). It’s the grammatical subject:

• 비가 그치다 = the rain stops (subject + intransitive verb)
  You wouldn’t use 비를 here because there’s no verb taking rain as a direct object.

Could it be 비는 instead of 비가?