事故(shì gù) - accident, mishap (serious) in Mandarin

事故 (shì gù) is an accident of the serious kind: on the roads, in a factory, at a building site. It is the word in news reports and official language, and it implies damage or injury and usually an investigation.

The verbs that go with it are worth learning as a set. 出事故 and 发生事故 both mean an accident occurs, and the classifier is 起 rather than 个: 一起交通事故.

For an English speaker the trap is that accident covers two quite different things. Something done by accident, unintentionally, is not 事故 at all: that is 不小心 or 意外. Say 我事故打破了杯子 and you have reported an industrial incident involving a teacup.