“出轨”有两种意思，一种是指列车出轨，一种是指情侣间的背叛。
列车出轨用derail [dɪˋrel] 。
例如：
A train derailed in India and killed at least 150 people.
有辆火车在印度出轨，至少150人死亡。
The train derailment was caused by faulty brake system.
这次的火车出轨事件是刹车系统故障引起。
情侣间的背叛则要用cheat on someone。
例如：
Mike's girlfriend is cheating on him with her ex.
麦克的女友正背着他和前任男友交往。
Laura's husband cheated on her with his secretary.
萝拉的丈夫和他的秘书出轨。
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