【Accident】

1）an unpleasant event, especially in a vehicle, that happens unexpectedly and causes injury or damage （可數名詞）；（交通）事故；意外遭遇；不測事件

例：He was killed in an accident. 他死于一次車禍。
One in seven accidents is caused by sleepy drivers. 每七次交通事故就有一次是駕車者困倦造成的。

2）something that happens unexpectedly and is not planned in advance （可數或不可數名詞）意外；偶然的事

例：Their early arrival was just an accident. 他們早到僅僅是偶然而已。
It is no accident that men fill most of the top jobs in nursing. 男人擔任護理中大多數最重要的工作絕非偶然。

【拓展】by accident ： it happens completely by chance 偶然，意外的

如： We met by accident at the airport.
我們在機場不期而遇。