无主句

The subjectless sentence

Some Chinese sentences actually do not have subjects (not with the subjects omitted). Most of them consist of a verb-object phrase generally describe natural phenomena. For example,

下雨了。
下雪了。
刮风了。

Some of these sentences indicate the emergence of a new situation. For example,

上课了，请大家不要再说话。
吃饭了，咱们先复习到这儿。