This is the 15187th most frequent Korean word.
방울을
"방울을" means "a drop" or "a bell" (depending on context, as it is a noun with particle).
In this sentence, '방울을' refers to a bell-like structure or small object that is part of something, in this case, a detail of the flower.
나는 방울을 체크하려고 꽃을 자세히 보았다.
I closely looked at the flower to check its bell.
Here, '방울을' represents a standalone bell, a common item that produces sound when shaken.
아이는 방울을 흔들며 소리를 들었다.
The child shook the bell to hear its sound.
In this usage, '방울을' refers to a droplet, representing a small quantity of liquid observed on the leaf.