Expressing "and then" with "yushi"
于是 is a conjunction used to express a continuation between two events. The second event is the direct result of the first event.
于是 is a conjunction that comes between two clauses. Its closest English equivalent would be "and then." Since 于是 can only be used to talk about the past, 了 is ofter used in the same sentence.
⋯⋯ ，于是 (+ Subj.) ⋯⋯ + 了
- 我 看 大家 都 买 了 ，于是 我 也 买 了 。I saw everyone was was buying. And then I bought it, too.
- 昨天 突然 下雨了 ，于是 我们 取消 了 野餐 的 计划 。It rained yesterday, so we cancelled the picnic.
- 网站上 的 票 已经 卖 光 了 ，于是 我们 买 了 黄牛票 。The tickets on the website were sold out. And then we bought the tickets from the scalpers.
- 他 的 英语 太差 了，于是 ，他 妈妈 给 他 请 了 一个 英语 家教 。His English is too bad. And then his mother hired an English tutor for him.
- 她 发现 男朋友 已经 结婚 了 。于是 ，她 马上 跟 他 分手 了 。She found her boyfriend's been married. And she broke up with her.
于是 Used with 就
于是 is often used with 就 to emphasize that the actions or events that come after 就 are immediately after the first event.
- 电影 太 暴力 了 ，我们 实在 看 不 下去 了 ，于是 就 走 了 。This movie was so violent and we couldn't bear watching it anymore. And then we left.
- 他 实在 太 懒 了 ，于是 老板 就 把 他 辞 了 。He was too lazy and then the boss fired him.
因此 vs. 于是
While they may seem very similar, 因此 is not quite the same as 于是. When using 因此, it acts as a conjunction that expresses the cause and effect. Because of the reasons in clause one, clause two reaches this result or conclusion.
- 因此 emphasizes a cause and effect relationship. 于是 emphasizes that the first event is closely followed by the second event.
- 于是 can only be used to recount events that happened in the past.
- 因此 is more formal and mostly used in writing. 于是 is more commonly used when speaking.
- 他 经常 随便 开玩笑 ，因此 ，大家 都 不 喜欢 跟 他 说话 。He often makes jokes recklessly. Therefore, people doesn't like to talk to him.
- 他 经常 随便 开玩笑 ，于是 ，大家 都 不 喜欢 跟 他 说话 。He often makes jokes recklessly, so people doesn't like to talk to him.
Sources and further reading
- HSK Standard Course 4下 (pp. 49) →buy
- 现代汉语虚词手册 (pp. 326) →buy
- 现代汉语八百词（增订本） (pp. 636) [ →buy]
- 对外汉语教学语法释疑201例 (pp. 362) [ →buy]