This is the 16686th most frequent Korean word.
사이로
"Sairo" (사이로): Between, in the space of, or through.
In this sentence, '사이로' means 'through the space between,' indicating movement between two objects, namely the mountains.
기차는 두 산 사이로 지나갔다.
The train passed through between the two mountains.
Here, '사이로' refers to relationships or connections between individuals, in this case, friends.
친구 사이로 오해가 생겼다.
A misunderstanding arose between friends.
In this usage, '사이로' describes light filtering through the gaps or spaces between objects, specifically the trees.