Chinese is a topic-prominent language. The notion of ‘topic’ plays a more important role than that of subject in explaining the structure of ordinary sentences. Often the initial part of a sentence sets up a topic ‘a matter of current interest or concern’ that is known to the hearer, hence definite in reference. The rest of the sentence the comment, is construed as being ‘about the topic’, that is, as conveying some information relevant to and being able to increase the hearer’s knowledge about the topic. The relationship between topic and comment is loose, open and pragmatic (Lambrecht, 1994). This means that, as long as the comment expresses something about the topic within a particular context, the sentence will be meaningful. For instance: 这鸡不能吃了。‘Zhè jī bù néng chī le’. The meaning of the sentence is dependent on the context. In the context where someone is talking about the freshness of the prepared chicken, the sentence means ‘The chicken cannot be eaten anymore’. The topic expression 这鸡‘zhè jī’ (this chicken) is the object of the VP 不能吃‘bù néng chī’ (cannot eat (cannot be eaten)). But in another context where one is talking about the health of the chicken that he is feeding, then the sentence means ‘The chicken cannot eat any more’ (it is so sick). In this interpretation, the topic expression 这鸡‘zhè jī’ bears the grammatical relation of the subject of the VP 不能吃了‘bù néng chī le’ (cannot eat). In both cases, since the comment supplies some information about the topic ‘the chicken’, the sentence is meaningful and well formed. In many other cases, the initial topic expression may not bear any grammatical or semantic relation with the VP in the comment, its relation with the comment can only be construed as a pragmatic relation of ‘aboutness’ and ‘relevance’, as shown: 图书馆不能吸烟。‘Túshūguǎn bù néng xīyān’ (You cannot smoke in the library, but literally: The library cannot smoke.), the topic 图书馆‘the library’ is not syntactically or semantically integrated into the predicate-argument structure of the sentence.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.