Fēijī shàng ren zhēn duō.
(There were many people on the airplane.)
Xiàng bízi cháng.
(Elephants have long noses.)
Sentences (a, b) exemplify ‘S-P predicate construction’. In each sentence, there also appear two NPs. The first NP is definite or generic in reference, the second is followed by a predicate. On close inspection, we can see that the two nouns are related as whole-part or in some other way, but the two juxtaposed NPs cannot constitute a proposition. However, if we consider the segment beginning with the second NP as a unit, it immediately dawns on us that the unit actually stands in the ‘topic of’ relation to the first NP. Thus we see that the whole sequence of words constitutes a sentence consisting of two parts: a topic realized by the first definite NP and a comment realized by a clause with the second NP as its subject, the two cohering with each other as a complete thought, meaning ‘There are many people on the airplane’. A sentence so constructed is called S-P predicate construction, as the comment or the predicate of the first topic NP is composed of subject and predicate.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles.
New York: Peter Lang.