The potential complement is one kind of important complements in Chinese language that the students need to master when they come to study in China. From the perspectives of structure and meaning, the potential complement can be divided into three classifications, the first of which is the structure verb1 + 得/不 + verb2/adjective, indicating that there is no condition or ability to finish certain action or realize certain result. For example, you can say 刚刚到北京我什么也听不懂.
The negative forms of potential complement such as 看不懂、听不明白/不进去/出不来 are often applied to indicate to fail to realize certain result because of the subjective or objective conditions. As a matter of fact, we call it the basic form of potential complement because when can only use the potential complement to express the meanings mentioned above in Chinese language. For instance, 大厅里人太多太挤，我们进不去. If we use 不能…, it will be not corresponding with the expression habit in Chinese like 大厅里人太多太挤，我们不能进去.
Some students may have seen the sentences of the second condition verb+ 得/不 +了 when they study in summer program in China like 没有钱我们就干不了. It is used to indicate whether there is possibility to realize certain results. 了is to indicate to have ability or condition to realize the results. In this case, 了has the meaning of finish. For example, 这么大的西瓜，谁吃得了？我克吃不了.
The last but not the least form is verb/adjective +得/不得, indicating to make a judgment whether it is possible to realize the goal when considering the result. It usually appears with the form of affirmative questions, negative questions as well as negative forms to warn or advise the other side should not do something, or some bad effects will be caused if certain action is processed. For instance, 这种书。小孩子看得看不得？得can be used both after verb and adjective like 那个女孩子你可惹不得.