站在旁邊、學會整個角色
兩個用法共用同一個畫面，差別只在英文把鏡頭對準人，還是對準那份工作。
noun · B2
An actor who has learned another actor's part and is ready to go on stage in that part if the usual actor is ill or cannot appear.
替角；候補演員
核心畫面
Picture someone standing in the wings, night after night, mouthing every line of a part they are not playing. They know the moves, the pauses, the moment the door opens. Most evenings they go home without setting foot on the stage. The whole word lives in that position: fully prepared, and not first in line. English only needs to decide whether it is naming the person standing there, or naming what that person is doing.
可以想成一個人站在舞台側邊，一晚又一晚，跟著默念一個不是自己的角色的每一句台詞。走位、停頓、門什麼時候打開，他全都記…更多收起
可以想成一個人站在舞台側邊，一晚又一晚，跟著默念一個不是自己的角色的每一句台詞。走位、停頓、門什麼時候打開，他全都記得。多數的晚上，他沒踏上舞台就回家了。這個字整個活在那個位置上：準備得很完整，但排在第二順位。剩下的，只是英文要指「站在那裡的人」，還是指「那個人在做的事」。From the word’s history
Formed from under- plus study: the person who studies a part from below or beside the one who plays it.
由 under-（在底下、在旁邊）加上 study（學）組成：在主角旁邊、把那個角色學起來的人。這個組合也把它的語氣說清楚了——準備是完整的，位置是第二順位的。
packet Wiktionary etymology tree for understudy (kaikki:3f6f69a190036ae4:881519561), which builds the word from English under- and study (Latin studeō).
One branch