被字句
The bei-construction

第五级里你已经说过“我的车被人开走了”“书被拿走了”“他被老师批评了”。那时候你是照着样子说的；现在给这个句式一个名字——被字句，再看看它为什么非这样不可。

You have been saying these since level 5: 我的车被人开走了, 书被拿走了, 他被老师批评了. Back then you copied the shape. Now the shape gets its name — 被字句 — and you find out why it insists on being built exactly this way.

施事是动作的发出者，受事是动作落到的那个人或者东西。主动句从施事说起：“弟弟打破了杯子”；上一课的把字句也从施事说起：“弟弟把杯子打破了”；只有被字句从受事说起。三句话说的是同一件事，不同的是句子先关心谁。

The 施事 is the one the action comes from; the 受事 is the person or thing it lands on. An active sentence starts from the agent, and so does the 把 sentence of the last lesson — only the 被字句 starts from the patient. Three sentences, one event; what changes is who the sentence cares about first.

不知道是谁做的，或者不必说是谁做的，“被”后面就空着：“我的自行车被偷了”。“让”“叫”是口语里表示被动的词，它们后面一定要跟一个名词；实在不知道是谁，就说“让人……”“叫人……”。“给”也有同样的用法，更随便一些。

When you do not know who did it, or it does not matter, the slot after 被 simply stays empty: 我的自行车被偷了. 让 and 叫 are the spoken passives and they will not tolerate an empty slot — if you truly do not know, say 让人…, 叫人…. 给 does the same job, more casually still. All three belong to 口语, spoken Chinese; 被 is the one you write.

这一条跟把字句完全一样：两个句式都要说出“后来怎么样了”。所以动词后面常常带结果补语（打破、吃完、拿走），或者趋向补语（开走、带来），或者一个“了”。光说“杯子被打”，听的人会等着下文。

This is exactly the requirement you met with 把: both constructions exist to report what became of something, so the verb has to carry a result — a resultative complement (打破, 吃完, 拿走), a directional one (开走, 带来), or at the very least 了. 杯子被打 leaves your listener waiting for the rest.

被字句传统上说的是不如意的事：车被偷了、杯子被打破了、他被批评了。这就是为什么“他被表扬了”从前听着有点儿别扭。现代书面语受了翻译的影响，中性的甚至好的事情也用被字句了——“他被选为班长”“这本书被译成了十种文字”，今天都很正常。口语里那种不如意的味道还在，事情要是不坏，多数人就直接说主动句。

Traditionally the 被字句 reports something 不如意 — unwelcome. That is why 他被表扬了 once sounded slightly odd. Under the influence of translation, modern written Chinese has widened it to neutral and even good news: 他被选为班长 and 这本书被译成了十种文字 are ordinary today. In speech the old flavour survives: if nothing bad happened, most speakers just use the active sentence.