今天的主力：荒唐到不可思議的決定
判斷力鬆脫的畫面，被搬到一個決定上，於是這件事本身看起來像瘋了。
noun · C1
Behaviour, a plan, or a situation that is completely crazy — so badly thought out that anyone looking at it can see it makes no sense.
荒唐／瘋狂之舉
核心畫面
One way to hold lunacy: a mind that has come loose from ordinary judgement. Older writers put that under the moon, and used the word for illness and for a court ruling. Modern English keeps the but drops the illness, so today it usually lands on a plan so far from sense that everyone watching shakes their head.
lunacy 可以想成判斷力整個鬆脫的狀態。舊時代的人把這種鬆脫連到月亮上，所以這個字以前指疾病，也指法院的一種認定…更多收起
lunacy 可以想成判斷力整個鬆脫的狀態。舊時代的人把這種鬆脫連到月亮上，所以這個字以前指疾病，也指法院的一種認定。今天的英文留下了鬆脫的畫面，卻放掉了疾病的部分。於是現在多半用來說一個離譜到大家搖頭的決定。From the word’s history
The packet gives lun(atic) + -acy, and the source's own gloss ties the older sense to the phases of the moon — which is why the historical branches are about illness while today's use is about crazy decisions.
證據裡寫的是 lun(atic) 加 -acy，而來源自己的釋義把舊意思連到月亮的圓缺。這正好說明為什麼歷史上的分支講的是疾病，而今天的用法講的是荒唐的決定。再往前的拉丁字根不在這份證據裡，這裡不作宣稱。
packet evidence: Wiktionary etymology_text for lunacy (From lun(atic) + -acy) and its gloss 'A cyclical mental disease, apparently linked to the lunar phases', source_ref kaikki:3f6f69a190036ae4:425282214:12281
Two branches
舊文本裡的意思：疾病與法律責任
同樣是判斷力鬆脫，但舊時代把它當成一種病況，而不是一次糊塗的選擇。這兩個意思是讀舊書時才會碰到的。
noun · C2
Serious mental illness. This is an old-fashioned use, met mainly in older books, older laws, and the names of old institutions; present-day writing says mental illness instead.
（舊用法）精神失常