1. 随机事件：chance 偶然性;偶然的 | chance event 随机事件 | chance move 随机步

2. 不确定结点：chance error == 机误 | chance event == 不确定结点 | chance failure == 偶然事故,偶然故障,意外事故

noun

1. anything that happens suddenly or by chance without an apparent cause

e.g. winning the lottery was a happy accident
the pregnancy was a stroke of bad luck
it was due to an accident or fortuity

Synonym: accidentstrokefortuity