Why We Can't Say一个人走了 in Chinese

It is important for the students who study in Mandarin language courses in China to know that it is incorrect to say 一个人走了. Firstly, let’s see some comparative examples like 你姐姐找你，一个人找你 and 有个人找你. After the comparison, you can find that the subject is needed in Chinese language no matter it is the doer of the action in the sentence or the object of the action. Even though a certain noun functioned as the subject, it also indicates the specific thing. For instance, if you say 学生来了, it means you and the hearer know the so-called 学生.

Besides, in the sentence structure, the quantity indicates the uncertain things. Therefore, it is not put in the beginning of the sentence as the subject. When you learn Chinese language, you should add 有 before it and make it the object of 有. In this way, the whole sentence is no longer the subject-predicate sentence, but the pivotal sentence. And in the sentence 一个人走了, the structure一个人is uncertain. Therefore, it can’t function as the subject and accordingly the sentence is incorrect.

However, there are also some special sentences in Chinese language that the subjects imply the uncertain things but still correct. The followings are some typical examples, 一个人也没来，一本书都没丢，一锅饭吃六个人and 十个人吃一锅饭. For the foreigners who attend to school to study in China, they may be told that the subjects of the former two sentences have a wide and general meaning indicating all so and no exception. Usually, they are followed by the adverbs也or都. That is to say,一个人implies anyone.

However, the latter two sentences are different, in which both the subjects and objects are the quantity structures, forming the quantity comparison relation. And the places can be changed with each other. We can say both 一锅饭吃六个人 and  六个人吃一锅饭. The most important thing you should know is the uncertain quantity can‘t be subject except for several special conditions.