The verb is the most ‘central’ element in the sense that, first, its position is normally medial rather than initial or final. It is preceded by the subject and/or an adverbial (if present), and followed either by the object (indirect and direct) or by the complement, or by both. Second, the verb element is normally obligatory, and it is not subject to movement to a different position in a sentence. Semantically, verbs describe states or events, which involve participants, so verbs presuppose the presence of noun phrases that refer to the participants in events, thus they help to determine what other elements must occur. The type and number of participants for each verb are determined to a large extent by the meaning of the verb. Apart from participants, adverbials which provide information about the circumstances such as time, place, manner, etc. of an event are also related to the verb. In addition, a number of grammatical elements that denote semantic concepts such as aspect, tense, modality, etc. are all closely associated with events and hence tend to appear with verbs in most languages (Chinese has aspect but not tense). For all these reasons, “…the verb phrase of a sentence in any language is that part of the simple sentence of which the nucleus is the verb” (Li and Thompson, 1981: 139). Thus, in our discussion, the positions of other clause elements are analyzed in terms of conceptual principles with respect to that of the verb—the nucleus of a clause; therefore we will call it the head verb.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.