by accident

偶然

The discovery was a happy accident.

這個發現是機緣巧合的。

accident and emergency

(Brit.)denoting a hospital department concerned with the provision of immediate treatment to people who are seriously injured in an accident or who are suddenly taken seriously ill

(英)急診室

an accident waiting to happen

(informal)a potentially disastrous situation, typically caused by negligent or faulty procedures

(非正式)（尤指由于疏忽大意或程序錯誤而造成的）隱患

accidents will happen in the best regulated famili

(proverb)however careful you try to be, it is inevitable that some unfortunate or unforeseen events will occur

(諺)家規再嚴，事端難免

problems like these should not occur, but accidents will happen.

這類問題不應出現，但保不定會有意外的。

without accident

safely

安全地

he was able to stop the train without accident.

他能安全地停住火車。