rank and file

為甚麼 rank and file 解作士兵、員佐級、普通成員或一般大眾呢？
原來 rank 指橫列(side by side)，而 file 指縱列 (one behind another)。在軍隊裡，士兵列隊時需要橫列、縱列或縱橫並列，而軍官卻不用這樣做。因而，rank and file就用來喻指普通士兵。後來這一短語又進一步引申成百姓或普通成員等。
例子：
The party's rank and file are beginning to question the prime minister's choice of advisers.
Most rank and file police officers rejected the new pay offer.