玩得开心(Wán de kāixīn, have a good time)
得(de) – the complement marker
English speakers love to wish someone to have a good time or to have fun which in Chinese is玩得开心(Wán de kāixīn). Here得is structural particle: used after a verb (or adjective as main verb), linking it to following phrase indicating effect, degree, possibility etc. This one is described as shuāngrén de, as the 彳 radical is colloquially known as shuāngrén (‘double person’).
There are two kinds of complement that may use 得: degree and potential. Both of them are used to modify verbs.
Degree complement The degree complement assesses the extent or quality of an action, or the state of things after it. For example:
她吃得很快。(tā chī de hěn kuài. She eats very quickly.)
你汉语说得很流利。(Nǐ hànyǔ shuō de hěn liúlì. You speak Chinese quite fluent.)
Here, ‘很快’ is the quality of the verb ‘吃’ and it’s marked by 得. 得 directly follows the verb in a sentence. It can also describe what happens after the action of a verb or adjective takes place:
他高兴得跳起来了。(Tā gāoxìng de tiào qǐláile. He was so happy he started jumping up and down.)
This often matches up with the English structure “so (adjective) that … .”
The rules get a lot more complex when you start adding in negatives, questions and objects for the verbs, but this article is just a summary.
Key point: the degree complement is used to assess or describe verbs.
The potential complement indicates whether or not something can happen, or someone has the ability to do something. As the name suggests, it’s all about the potential of something. For example:
我看得懂中文。(wǒ kàn de dǒng zhōngwén. I can read (and understand) Chinese.)
他听得很清楚。（Tā tīng de hěn qīngchu. He can hear well/clear.）
This sentence is not about whether or not you have read some Chinese, it’s about whether you understand it if or when you do. It describes your ability in general; your potential to read Chinese.
Only the positive form of the potential complement uses 得. In the negative form, 得 is replaced by 不(bù):
我看不懂中文。(wǒ kàn bu dǒng zhōngwén. I can’t read (and understand) Chinese.)
他听不清楚。（Tā tīng bù qīngchu. He can’t hear well/clear.）
Key point: the potential complement is about possibility and ability.