“Broke a promise”是一个动词短语，源自英语，意指未能履行或违背先前作出的承诺或保证。这个短语强调了对某人或某事的不忠或失信行为，通常带有负面的道德或情感含义。

**用法：**

1. 作为动词短语，"broke a promise"常用于描述一个人未能按照之前所说或同意的事情去做。

2. 可以用来表达失望、愤怒或背叛的情绪，尤其是在人际关系或合同义务中。

3. 在句子中，"broke a promise"通常用作过去式，表示已经发生的违约行为。

**例句：**

1. She broke a promise to visit her grandmother, which made her feel guilty. (她违背了去看望祖母的承诺，这让她感到内疚。)

2. Despite his assurance, he broke a promise not to tell anyone about the secret project. (尽管他保证了，但他还是违背了不告诉任何人这个秘密项目的承诺。)

3. When he didn't show up on their anniversary, she knew he had broken a promise. (当他在周年纪念日没有出现时，她知道他已经违背了承诺。)

**同义词辨析：**

1. **Failed to keep a promise** - 同样表示未能遵守承诺，但语气稍微温和一些，更侧重于结果而不是故意的行为。

   例句：He failed to keep a promise to help with the charity event, leaving them short-handed. (他未能履行帮助慈善活动的承诺，使他们人手不足。)

2. **Breached a commitment** - 强调的是对某项承诺的侵犯，通常在正式或法律语境中使用。

   例句: The company breached a commitment to its employees by cutting their benefits without notice. (公司违背了对员工的承诺，未经通知就削减了福利。)

3. **Didn't fulfill a pledge** - "Pledge"有誓言或保证的意思，因此这个短语暗示了未能实现庄严的承诺。

   例句: The politician didn't fulfill his pledge to reduce taxes, causing public outrage. (这位政客没有兑现减税的承诺，引发了公众的愤怒。)

4. **Backed out of an agreement** - 指从一项协议或约定中退出，通常涉及到双方或多方的约定。

   例句: They backed out of the business agreement at the last minute, leaving the other party in a difficult situation. (他们在最后一刻退出了商业协议，让另一方陷入了困境。)