1For objects to be stacked on top of each other, forming layers.
机の上に本が何冊も重なっている。
Several books are piled up on the desk.
落ち葉が地面に重なって積もっていた。
Fallen leaves had piled up in layers on the ground.
皿を重なるように積んで棚にしまった。
I stacked the plates on top of each other and put them away in the cupboard.
2For events or matters to happen one after another, or to build up in quantity.
今月は出費が重なって、家計が苦しい。
This month expenses have piled up, and money is tight.
不運が重なって、彼は仕事を失ってしまった。
A string of bad luck piled up, and he ended up losing his job.
疲れが重なって、ついに体調を崩した。
Fatigue accumulated, and he finally became ill.
3For two or more things to overlap or happen at the same time.
友人の結婚式と出張の日程が重なってしまった。
My friend's wedding overlapped with my business trip schedule.
二つのイベントが同じ週末に重なるのは避けたい。
We want to avoid having the two events overlap on the same weekend.