Think of something that was put together coming apart again into the pieces it was made from. The word is compose with de- in front of it, and de- runs the action backwards. Sometimes time and weather do the taking-apart, and we call that rotting. Sometimes a person, a current or a machine does it on purpose, and we call that separating. Either way the picture is the same: a whole thing stops being one thing and becomes its parts.
可以想成一個組好的東西，又被拆回它原來的零件。這個字就是 compose（組合）前面加上 de-，而 de- 的作用是把動作倒著跑。有時候拆解的是時間和天氣，那就是腐爛：落葉、果皮慢慢散成土。有時候拆解的是人、電流或一台機器，而且是刻意的，那就是分解：水分解成氫和氧，任務分解成步驟。兩邊的畫面其實一樣——一個整體不再是一個整體，變回它的零件。
From the word’s history
Borrowed from Middle French décomposer, and analysable in English as de- + compose. The core picture is literally 'un-compose'.
借自中古法文 décomposer，在英文裡可以直接拆成 de- 加 compose。核心畫面就是字面上的「反組合」。
Wiktionary etymology supplied in this packet (source_ref kaikki:3f6f69a190036ae4:394120821:18292)
登入就可以看每一支怎麼連回核心畫面。