1
be faithless to sb
faithless 常指对配偶或盟友不忠，比 unfaithful 更正式、更具贬义。
He was faithless to his wife.
他对妻子不忠。
不忠的；背信弃义的
先理解核心含义，再看它在真实句子里的用法。
不忠的；背信弃义的
traitorous; having the character of a traitor
He was faithless to his wife.
他对妻子不忠。
缺乏信仰；缺乏信念。
Lacking faith; lacking belief in something.
具有叛徒性格或特征的
having the character of, or characteristic of, a traitor
不相信上帝、宗教或类似意识形态的。
Not believing in God, religion, or a comparable ideology.
不忠的(指人对伴侣)。
Unfaithful (said of people, towards their partners)
After he broke his word, she called him faithless and left.
他食言后，她称他毫无信义并离开了。
AI contextual example
A faithless friend told my secret to the whole class.
一个不忠的朋友把我的秘密告诉了全班。
AI contextual example
He became rich and faithless to his old friends, never calling them again.
他富有了，对老朋友背信弃义，再也不给他们打电话。
AI contextual example
the faithless Benedict Arnold
背信弃义的本尼迪克特·阿诺德
WordNet
faithless 常指对配偶或盟友不忠，比 unfaithful 更正式、更具贬义。
He was faithless to his wife.
他对妻子不忠。
faithless 作定语时强调此人背叛了信任，常见搭配如 faithless friend、faithless husband。
She was betrayed by a faithless friend.
她被一个背信弃义的朋友背叛了。
Not this
She called him a faithless.
Use this
She called him faithless.
faithless 是形容词，不能直接当可数名词用。不能说 a faithless，应去掉冠词，把形容词用作宾语补足语，或说 a faithless person。
Not this
He has no faith to his wife.
Use this
He is faithless to his wife.
这是受中文“对某人不忠”的影响。faith 作名词表示“信任”时搭配 in，不是 to；要表达“不忠实”不能用 have no faith to，而应用形容词 faithless，后接 to 表示“对……不忠”。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
不忠的朋友
She was heartbroken when her faithless friend spread rumors about her.
当她不忠的朋友散布关于她的谣言时，她心碎了。
不忠的恋人
He left his faithless lover and moved to another city.
他离开了不忠的恋人，搬到了另一个城市。
背信弃义的行为
Faithless behavior like breaking promises can ruin a reputation.
像违背承诺这样的背信弃义行为会毁掉名声。
不忠的仆从
The lord punished his faithless servant for betraying the household.
主人惩罚了背叛家宅的不忠仆从。
失信选举人
Some states fine a faithless elector who fails to vote for the pledged candidate.
一些州会对未按承诺投票的失信选举人处以罚款。
唉！这又不信又悖谬的世代啊，我在你们这里要到几时呢？
The faithless general betrayed his country for gold.
那个不忠的将军为黄金背叛了自己的国家。
Use faithless naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
记忆联想：faith（信任/信仰）加上 less（没有），对人毫无 faith，就是 faithless（不忠、背信）。
语域：formal 常见场景：文学或正式文本、历史或政治论述、形容背弃誓言或信念 该词通常用于较正式或带有文学色彩的语境，多指对信仰、誓言或忠诚的背叛，口语中较少使用。
No common words rhyme exactly with faithless. The -less words below share only the suffix. Shameless, blameless, and nameless match the /eɪ/ vowel but differ in the following consonant (/m/ vs /θ/), so they are not rhymes. Helpless, restless, and breathless have different vowel sounds entirely.
Dictionary facts from ECDICT, WIKTIONARY.