1
be demented
常用作表语，表示状态。
He was demented after the accident.
事故后他精神错乱了。
发狂的；精神错乱的
先理解核心含义，再看它在真实句子里的用法。
发狂的；精神错乱的
insane; mad
He was demented after the accident.
事故后他精神错乱了。
精神错乱的；精神病的
Insane; mentally ill.
精神错乱的
affected with madness or insanity
患有痴呆症的
Having dementia.
By the end of the week, the constant noise made everyone feel demented.
到周末时，持续的噪音让每个人都觉得要发狂了。
The villain gave a demented laugh before disappearing into the dark.
那个恶棍发出一阵疯狂的笑声，然后消失在黑暗中。
She had a demented look in her eyes when she talked about revenge.
她谈到复仇时，眼中带着一种精神错乱的神情。
常用作表语，表示状态。
He was demented after the accident.
事故后他精神错乱了。
用作定语修饰名词。
She had a demented look in her eyes.
她眼中流露出疯狂的神色。
表示变为精神错乱的状态。
The old king went demented in his final years.
老国王在晚年发疯了。
Not this
The constant noise demented me.
Use this
The constant noise drove me demented.
demented 是形容词，不能作为动词使用。正确用法是搭配动词 drive 或 make，构成 drive/make someone demented 结构。
Not this
She is a demented.
Use this
She is demented.
demented 是形容词，不能直接用作可数名词。应直接用作表语形容词，或使用 a demented person 这类短语。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
精神错乱者
The demented person was taken to a psychiatric hospital.
那个精神错乱的人被送进了精神病医院。
疯狂的行为
His demented behaviour frightened the children.
他疯狂的行为吓坏了孩子们。
变得精神错乱；患上痴呆
She became demented after the accident.
事故发生后她变得精神错乱。
精神错乱状态
In his demented state, he could not recognize his own family.
在精神错乱的状态下，他认不出自己的家人。
癫狂的笑声
A demented laughter echoed through the empty hall.
一阵癫狂的笑声在空荡荡的大厅里回荡。
Use demented naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
看到 demented 就想到 dementia（痴呆）：记忆的线断了，人便精神错乱。
语域：mixed 常见场景：临床医疗语境、日常口语夸张表达 该词表示“精神错乱的；痴呆的”时，语域随语境变化：正式/医疗描写与口语夸张用法都存在。直接用于人可能显得冒犯；通常口语中更常说 crazy 或 out of one’s mind，医学上常说 with dementia。
All the words above rhyme with 'demented' (/dɪˈmɛntɪd/): they contain the stressed vowel /ɛ/ followed by /ntɪd/ (or /tɪd/ after an n). Be careful with lookalikes such as 'demanded' (/dɪˈmɑːndɪd/) or 'decided' (/dɪˈsaɪdɪd/)—they end in '-ed' but have a different vowel sound, so they do not rhyme.
Dictionary facts from ECDICT, WIKTIONARY.