1
be unintentional
系表结构，表示主语是无意的。
The error was unintentional.
这个错误是无心的。
无意的；非故意的；不经意的
先理解核心含义，再看它在真实句子里的用法。
无意的；非故意的；不经意的
not done on purpose; without intention or deliberate planning
The error was unintentional.
这个错误是无心的。
非故意的,非有意的；无心的,不经意的。
Not intended or deliberate; inadvertent; unwitting.
It was an unintentional mistake; I didn't mean to delete your file.
那是个无意的错误；我不是故意删除你的文件的。
She gave him an unintentional push as she turned around quickly.
她快速转身时无意中推了他一下。
The program's side effects were unintentional, but users still noticed them.
该程序的副作用并非有意为之，但用户还是注意到了。
系表结构，表示主语是无意的。
The error was unintentional.
这个错误是无心的。
定语位置，修饰名词。
She made an unintentional mistake.
她犯了一个无心的错误。
强调某方的行为是无意的。
The oversight was unintentional on the part of the manager.
这个疏忽在经理方面是无心的。
Not this
It was an unintentionally mistake.
Use this
It was an unintentional mistake.
形容词性错误：unintentionally 是副词，不能修饰名词 mistake；应使用形容词 unintentional。
Not this
He made an intentional error, but he didn't mean to.
Use this
He made an unintentional error, but he didn't mean to.
词义混淆：intentional 表示“故意的”，与句意“不是故意的”矛盾；应使用 unintentional 表示“无心的”。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
无心的错误
It was an unintentional mistake, but I still apologized.
那是个无心的错误，但我还是道歉了。
无意的伤害
The article caused unintentional harm to the community.
这篇文章给社区造成了无意的伤害。
无意的冒犯
He apologized for any unintentional offense his words might have caused.
他为自己所说的话可能引起的无意冒犯而道歉。
无意的幽默
His serious speech was full of unintentional humor.
他严肃的演讲充满了无意的幽默。
非本意的体重下降
Unintentional weight loss can be a sign of an underlying illness.
非本意的体重下降可能是潜在疾病的征兆。
Use unintentional naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
un-表示“不”，intentional是“有意图的”，合起来即“没有意图的”。联想不小心踩到别人脚时，那就是unintentional。
语域：neutral 常见场景：日常交流、书面说明 通常为中性词，多用于描述并非有意为之的行为或结果，在正式与非正式场合都比较常见。
与 unintentional 真正押韵的词是 intentional、conventional、dimensional、attentional，重读元音都是 /ɛ/，后面都接 /nʃənl/。拼写相似的 national（/ˈnæʃənl/）和 rational（/ˈræʃənl/）重读元音是 /æ/，并不押韵。
Dictionary facts from ECDICT, WIKTIONARY.