그러다

그러다

"그러다" means "to do so" or "to act like that."

Here "그러다" links the sequence of events, transitioning to the sudden rain.

그러다가 갑자기 비가 내렸어요.

And then suddenly it started to rain.

Here "그러다" (in "그래서") shows the reason leading to the action of waiting.

친구가 늦게 온다고 그래서 기다렸어요.

My friend said they would be late, so I waited.

In this case, "그러다" refers to continuing an undesired behavior.

그렇게 계속 그러면 안 돼요.

You shouldn't keep doing that like that.