讓人算一算就縮手的東西
從日常尺度到國家尺度，都是同一個機制：讓對方預見代價，因而放棄。
something that discourages action · noun · C2
Something that makes people less willing to do an action, because they can see it will be hard or will bring a bad result.
嚇阻
核心畫面
Picture someone about to do something — and then they stop, because they can see what it would cost them. A deterrent is the thing that makes them see that and hold back.
有人正要動手做一件事，腳步卻在最後一刻停住了——因為他看見了後果。讓他看見、讓他縮手的那樣東西，就是 deterre…更多收起
有人正要動手做一件事，腳步卻在最後一刻停住了——因為他看見了後果。讓他看見、讓他縮手的那樣東西，就是 deterrent。這裡有個很重要的細節：deterrent 不是用力量擋住他，而是讓他自己算了一下、決定不要。所以它作用在事情發生之前，靠的是「對方會怎麼想」。門口那盞感應燈之所以有效，不是因為它擋得住小偷，而是因為小偷看見它就轉身走了。From the word’s history
From Latin dēterrēns, present participle of dēterrēre 'to frighten off' (de- 'away' + terrēre 'to frighten'), the same terrēre behind terror and terrify.
這個字借自拉丁文 dēterrēns，來自動詞 dēterrēre——字面是「把人嚇開」（de- 離開 + terrēre 使害怕）。terrēre 也就是 terror、terrify 背後的那個字根。知道這件事之後，deterrent 的運作方式就很清楚了：它不是物理上的阻擋，而是讓對方心裡先怕、先算，然後自己退開。中文常用的「嚇阻」兩個字，剛好把這個字源保留得很完整。
Wiktionary (deterrent / deter, from Latin dēterrēre)
One branch
原始詞典資料2 筆記錄
以下是外部詞典記錄的用法，原文照列，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。
deterrentadj/dɪˈtɛɹənt/
- 1
Serving to deter, preventing something from happening.
deterrentnoun/dɪˈtɛɹənt/
- 1
Something that deters.
- An extension of the system to serve new housing estates on the outskirts of the city, at an estimated cost of about £4,000,000 a mile, is being considered, but the narrow gauge, small clearances, and short platforms are deterrents.
- Along with trial by ordeal, hanging was the most effective deterrent that could be devised in an age without police or prisons.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。