1. left-hand rule：right-hand rule 右手定则 | left-hand rule 左手定则 | slip 转差率
2. left-handed system：lateral system 横向支撑系统;支渠系统 | left-handed system 左手定则 | levee system 堤防系统
3. Fleming's rule for motors; left-hand rule：fixed phase 定相 | Fleming's rule for motors; left-hand rule 左手定则 | flip-flop circuit 正反电路