短语词组短語null data set [計]空數據組;空數據集;繙譯null off set 零點偏移null -set 零集function theoretic null -set [數]函數論的零集function -theoretic null-set 函數論的零集null set of class [數]類的零集l null set l 零集null off -set 零點偏移;零點漂移 返回 null set