回不去的改變
最直接的核心用法：狀態變了，而且沒有回頭路。
cannot be undone · adjective · C2
Used about damage or change that is so great that you cannot put things back the way they were.
不可逆的
核心畫面
Hold it as: a one-way door. Something has changed, and there is no path back to how it was — not because nobody tries, but because the way back does not exist.
一扇只能往一個方向開的門。ir-（不）+ reverse（倒回去）+ -ible（能夠）——「倒不回去的」。事情走過…更多收起
一扇只能往一個方向開的門。ir-（不）+ reverse（倒回去）+ -ible（能夠）——「倒不回去的」。事情走過去了，就沒有回頭的路；不是沒有人想倒回去，是那條路根本不存在。像打翻的牛奶、燒掉的照片、按下去就送出的訊息：時間可以繼續往前，但那個原本的狀態已經不在了。From the word’s history
Simply ir- (not) + reversible: 'not able to be turned back'. The modern core is the literal sum of its parts.
就是 ir-（不）加上 reversible（可以倒回去的），字面意思「不能被倒回去」。這個字的現代核心跟它的組成完全一致，拆開來看就懂——這也是為什麼學會這個 ir- 前綴，irregular、irrelevant、irresponsible 一起就好認了。
Wiktionary etymology tree supplied in the payload (ir- + reversible)
Two branches
好不了的身體狀況
同一扇單向門，把場景縮到身體上：健康的狀態走過去了，就回不到原來的健康。
incurable, permanent (illness) · adjective · C2
Used about an illness or a bad condition of the body that will not get better and cannot be made well again.
無法復原
原始詞典資料3 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。
irreversibleadj/ˌɪr.ɪˈvɜː.sə.bəl/
- 1
Incapable of being reversed or turned about or back; incapable of being made to run backwards.
- an irreversible engine
- 2
Incapable of being reversed, recalled, repealed, or annulled.
- an irreversible sentence or decree
- Manganism has been known about since the 19th century, when miners exposed to ores containing manganese[…]began to totter, slur their speech and behave like someone inebriated. The poisoning was irreversible, and soon ended in psychosis and death.
- 3
natural-sciencesphysical-sciencesphysicsIncapable of being reversed to the original state without consumption of free energy and increase of entropy.
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。