A noun phrase is referential when it is used to refer to an entity. The entity may be physical or conceptual, real or hypothetical, singular or plural, as exemplified below:
张三是我的朋友。‘Zhangsan is my friend.’
门口坐着一个女孩子。‘In the doorway was sitting a girl.’
这条香蕉我吃不下。 ‘This banana I can’ eat’
Noun phrases may be used nonreferentially. Some of the examples are shown below:
张三是工程师。‘Zhangsan is an engineer.’
The NP ‘engineer’ is not used to refer to any particular person.
Similarly, the object component of a verb-object compound is nonreferential, for instance,
我不会唱歌。‘I don’t know how to sing.’
Li, C. N., & Thompson, S. A. (1989). Mandarin Chinese: A functional reference grammar (Vol. 3). Univ of California Press.