插上電的東西
最字面的一組：真的有插頭，真的插進插座或另一台機器。
adjective · B2
Made so that you can connect it by pushing a plug in — either into an electrical socket, or into another piece of equipment.
插電式的、可插接的
核心畫面
One way to hold plug-in is to picture the moment a plug meets a socket. Two things that were separate a second ago are now working as one, and neither had to be opened, cut, or rebuilt to make it happen. Pull it back out and both are exactly as they were. Every use of the word keeps that moment: a heater that joins the wall, a microphone that joins a laptop, a car that joins the house overnight, a small program that joins a bigger one.
plug-in 可以想成插頭碰到插座的那一瞬間。一秒鐘前還是兩個分開的東西，現在一起運作了，而且誰都不必被拆開、剪線…更多收起
plug-in 可以想成插頭碰到插座的那一瞬間。一秒鐘前還是兩個分開的東西，現在一起運作了，而且誰都不必被拆開、剪線或重做。拔下來，兩邊又完全回到原樣。這個字的每一種用法都留著那個畫面：暖爐接上牆、麥克風接上筆電、車子整夜接上家裡、一個小程式接上一個大程式。From the word’s history
The supplied source marks plug-in as deverbal from the phrasal verb plug in: the action of pushing a plug into a socket was lifted whole and used as a name and as a describing word.
來源資料註明 plug-in 是從動詞片語 plug in 直接變來的（deverbal）。原本是「把插頭插進去」這個動作，整組被搬過來，一邊當名詞用，一邊當形容詞用。
Wiktionary entries supplied in this packet, etymology_text 'Deverbal from plug in.' (source_refs kaikki:3f6f69a190036ae4:1073808785 and :1073811960)
Two branches
插進軟體裡的那一塊
插座換成了一個程式：同樣是接上去多一項功能，拔掉主體也不受傷。
noun · B1
A small piece of software that you add to a program you already have, so that the program can do one extra thing — block ads, play a certain kind of file, take payments, and so on.
外掛程式、擴充功能