One way to hold this word: hold your hands up in front of your face and slide them apart sideways. That long, low is the whole word. Everything else follows from it: a machine can have that shape, a film can be made to fit that shape, and a sentence can say that something was done in that shape.
可以把 widescreen 想成用兩隻手在臉前面往左右拉開的那個長方形：又寬又扁，橫的比直的多很多。這個字說到底就只有這一個形狀。剩下的差別只是「誰是那個形狀」——機器是那個形狀、片子照那個形狀做、或者某件事是用那個形狀完成的。
From the word’s history
The word is simply wide plus screen, so the name already contains the picture: a screen that is wide.
這個字就是 wide（寬）加 screen（螢幕）拼起來的。名字本身已經把畫面講完了：一塊寬的螢幕。
Wiktionary, "widescreen"
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