“Happen to do sth”是一个英语短语,用来表示意外地或偶然地做某件事情,强调的是行为的偶然性和非计划性。这个表达通常用于描述一个没有预见或未计划的事件或行动。

**用法:**

在句子中,“happen to do sth”通常放在主语后面,动词不定式之前,用来表达意外发生的情况。例如:

1. I happened to meet my old friend in the park yesterday. (昨天我在公园里碰巧遇到了我的老朋友。)

2. She happened to be reading the same book as I was. (她碰巧正在读同一本书。)

**例句:**

1. It happened to rain when we decided to have a picnic. (我们决定野餐时,碰巧下雨了。)

2. I happened to catch the last bus, otherwise I would have been stuck at the station. (我碰巧赶上了最后一班公交车,否则我就被困在车站了。)

3. He happened to find a wallet on the street, which he promptly returned to its owner. (他偶然在街上发现了一个钱包,他立即归还给了失主。)

4. While walking down the street, I happened to hear my favorite song playing in a store. (走在街上时,我碰巧听到一家店里播放着我最喜欢的歌曲。)

**同义词与辨析:**

1. **Accidentally**: 这个词也表示意外或非故意的行为,但更侧重于动作的结果而非过程。例如:“I accidentally dropped my phone.” (我不小心把手机摔了。)

2. **By chance**: 这个短语和“happen to do sth”非常相似,都强调事情发生的偶然性。例如:“I met her by chance at the airport.” (我在机场偶然遇见了她。)

3. **Stumble upon**: 这个短语常用于发现或遇到意想不到的事物,有意外发现的意味。例如:“I stumbled upon an old diary while cleaning my attic.” (我在打扫阁楼时无意中发现了一本旧日记。)

4. **Come across**: 与“stumble upon”类似,"come across"也表示偶然发现或遇到。例如:“I came across an interesting article while browsing the internet.” (我在浏览互联网时偶然看到一篇有趣的文章。)