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it is lunacy to do sth
常用句式，表示强烈反对某行为。
It is lunacy to drive without a seatbelt.
不系安全带开车是疯狂愚蠢的行为。
精神错乱；疯狂
先理解核心含义，再看它在真实句子里的用法。
精神错乱；疯狂
the state of being mentally ill; madness
It is lunacy to drive without a seatbelt.
不系安全带开车是疯狂愚蠢的行为。
疯狂状态,精神错乱
The state of being mad, insanity
非常错误的事物
Something deeply misguided.
It would be sheer lunacy to drive across the desert without enough water.
没有足够的水就开车穿越沙漠简直是疯狂愚蠢的行为。
The plan to build a skyscraper on that unstable ground was dismissed as lunacy.
在那片不稳定的土地上建造摩天大楼的计划被视为疯狂愚蠢的行为而被否决。
Investing all your savings in a single stock is financial lunacy.
把所有积蓄都投在一只股票上是金融上的疯狂愚蠢之举。
常用句式，表示强烈反对某行为。
It is lunacy to drive without a seatbelt.
不系安全带开车是疯狂愚蠢的行为。
强调疯狂到极点。
The plan was sheer lunacy.
这个计划纯粹是疯狂愚蠢的。
Not this
He is lunacy.
Use this
He is lunatic.
lunacy 是名词，表示‘精神错乱’，不可用作形容词；应改用形容词 lunatic。
Not this
It was a lunacy.
Use this
It was lunacy.
lunacy 表示‘疯狂行为’时通常不可数，故不用不定冠词 a。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
十足的疯狂；十足的荒谬
Driving at that speed on icy roads is sheer lunacy.
在结冰的路上以那种速度开车简直是十足的疯狂。
近乎疯狂；近乎荒谬
Their decision to ignore the safety warnings borders on lunacy.
他们无视安全警告的决定近乎荒谬。
一时的疯狂；一时糊涂
I can only explain my actions as a moment of lunacy.
我只能把我的行为解释为一时糊涂。
把某事斥为荒谬至极
Critics dismissed the proposal as lunacy.
批评者认为该提案荒谬至极。
战争的疯狂
The novel captures the lunacy of war through its dark humor.
这部小说通过黑色幽默展现了战争的疯狂。
十足的疯狂；完全疯狂的举动
Driving that fast on an icy road is sheer lunacy.
在结冰的路面上开那么快简直是疯了。
Use lunacy naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
luna像lunar（月亮的），月圆之夜让人疯狂，lunacy就是疯狂状态。
语域：mixed 常见场景：formal prose、informal speech、news commentary lunacy 的语域随词义变化：在正式或文学语篇中多指“精神错乱”，在日常口语和评论文章中则更常用来夸张地形容“极其愚蠢的行为或想法”。具体含义需根据语境判断。
通常不可数，但有时可数，如 'different lunacies'。
Dictionary facts from ECDICT, WIKTIONARY.