动量补语 the action –measure complement

The action-measure word “次”or “遍”is often combined with a numeral and placed after a verb as the action-measure complement to express the frequency of an action. In addition to signifying the number of times,“遍” also denotes the whole process of an action from beginning to end. For example:
我上星期六打扫过一次。
这部小说我又看了两遍。
When the object of the verb is a noun, the action-measure complement should be placed before the object. When the object is expressed by a pronoun, the complement often comes after the object.

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Apart from indicating the frequency of an action, the action-measure complement “一下儿”is also used to indicate an action that is performed in a casual way, or that lasts for only a short while(refer to Note One in Lesson 7). Here are some examples:介绍一下儿，等一下儿。