A useful picture: instead of a straight line from A to B, the path bends and passes through something else on the way. 'Direct' means going straight at the target; 'in-' takes the straightness away. Whatever travels — an effect, a , or a meaning — arrives, but not by the straight line, and something sits in between.
From the word’s history
From Latin 'directus' (straight, laid straight, from dirigere 'to set straight, guide') with negative 'in-' and adverbial '-ly': literally 'not in a straight line'. Every modern use is that bent line applied to a different kind of path.
拉丁文 directus 就是「被拉直的」（來自 dirigere，把東西擺正、導直），加上否定的 in- 和副詞的 -ly，字面就是「不走直線地」。現代三個用法只是把這條彎掉的線放到三種不同的路徑上：因果的路、走動的路、說話的路。
Etymonline / Oxford English Dictionary entries for 'direct' (< Latin directus, dirigere) and the prefix 'in-'
登入就可以看每一支怎麼連回核心畫面。
原始詞典資料1 筆記錄
以下是外部詞典記錄的用法，摘錄並精簡格式，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
indirectlyadv/ˌɪn.dɪˈɹɛk(t).li/
- 1
In an indirect manner.
- His alcoholism had a direct effect on his health, and indirectly caused problems for others.
- At laſt a new Ceſſation of Hoſtilities upon theſe Points was reſolved on; yet the Hatred continues, and the War goes on, though more covertly, and more indirectly than before.
摘錄自 英文維基詞典 English Wiktionary，已精簡格式；依 CC BY-SA 4.0 授權使用，改動後的內容同樣以此授權提供。