a surprising and unexpected situation in which two things that are related happen at the same time, in the same place, or to the same people
同時性について言うわけですね。
It was a coincidence that two pandas gave birth to their each baby in a same day.
同じ日に二頭のパンダがそれぞれ出産した。
It’s no coincidence 偶然じゃない。
There is a coincidence of opinion among the board members.
メンバーの意見が同じである。