感覺不到刺激
最字面的一支：物理上的訊號進來，卻沒有引起任何變化。
physically unaffected · adjective · C1
Not changed or hurt by a physical effect or change, such as pain, heat, or cold.
不敏感
核心畫面
Picture a surface that does not register what touches it — press it, heat it, and nothing comes back. Insensitive is that missing response: the signal arrives, but nothing in the thing (or the person) picks it up.
一個「碰了也沒反應」的表面：你按它、加熱它、拿冰塊貼它，它就是不回應——訊號有到，但裡面沒有東西接收。insensi…更多收起
一個「碰了也沒反應」的表面：你按它、加熱它、拿冰塊貼它，它就是不回應——訊號有到，但裡面沒有東西接收。insensitive 講的就是這份缺席的反應。從一塊感覺不到痛的皮膚，到一個感覺不到別人難過的人，動作是同一個：外面有訊息傳來，而接收器沒有亮。這也解釋了為什麼它罵人的時候特別重——你說一個人 insensitive，等於說他身上那個該亮的燈沒亮。From the word’s history
in- (not) + sensitive, which traces to Latin sentire 'to feel, perceive'. The root is about feeling as reception — the same sentire behind sense, sentiment, and consent. Insensitive therefore names a failure at the receiving end, not at the caring end, which is why it can describe skin and people with the same word.
in-（不）+ sensitive，而 sensitive 追到底是拉丁文 sentīre「感覺、察覺」——sense、sentiment、consent 裡都是同一個字根。關鍵在於 sentīre 講的是「接收」這個動作，不是「在乎」這個心意。所以 insensitive 命名的是接收端的失靈，而不是道德上的壞：正因為如此，同一個字才能既描述一塊沒知覺的皮膚，也描述一個聽不出別人語氣的人。
Wiktionary: insensitive < in- + sensitive; ultimately Latin sentīre ('to feel, perceive')
Three branches
接不到別人的情緒
把失靈的接收器搬到人際場合：這次沒收到的訊號是別人的心情。
unaware of feelings · adjective · C1
Not noticing other people's feelings, or not taking care to notice them, so you do not see when they are upset or when something you do will upset them.
不體貼
不因外界而改變
同樣是訊號沒被接收，但這次沒被接收的是狀況本身——收到了也不調整。
unresponsive to surroundings · adjective · C1
Not paying attention to what is happening or to what people are saying, and so not changing what you do because of it.
不理會
原始詞典資料4 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。
insensitiveadj/ɪnˈsɛnsɪtɪv/
- 1
Expressing or feeling little or no concern, care, compassion, or consideration for the feelings, emotions, sentiments, or concerns of other people; inconsiderate or incompassionate.
- 2
Not expressing normal physical feeling.
- It is something like the way dame Nature gathers round a foreign body an envelope of some insensitive tissue which can protect from evil that which it would otherwise harm by contact.
- 3
Not expressing normal emotional feelings; cold; tactless; undiplomatic.
- 1895, Grant Allen, The British Barbarians Somehow, when Bertram Ingledew let it once be felt he did not wish to be questioned on any particular point, even women managed to restrain their curiosity: and he would have been either a very bold or a very insensitive man who would have ventured to continue questioning him any further.
- Oh I really should have known by the time you drove me home, / By the vagueness in your eyes, your casual good-byes, / By the chill in your embrace and the expression on your face, / That told me you might have some advice to give / On how to be insensitive.
- 4
Unreceptive, indifferent; displaying little openness or receptivity.
- This early rigidification and satisfaction with his own conclusions made him insensitive to new political and philosophical ideas.
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。