Abstract
This paper aims at teasing out the semantic and syntactic properties of thang 1 in six kinds of constructions. Thang 1 can occur as a circumstantial modal immediately after [u 7 /bo 5 ] v + NP in non-root clauses. When the NP is made implicit due to the constraint of information structure, u 7 /bo 5 may be changed into adverbs as adjuncts to root clauses featuring the modal thang 1 . Thang 1 as a modal can head a purpose clause as a complement of the root clause and form a modal stacking with other modals. Thang 1 is an important pivot to mediate the merger of the volitional negator m 7 and bare verbs in the formation of negative imperatives. The hierarchically lower position of thang 1 than why WH-words na 2 and thai 2 may be related to the induced interpretation of rhetorical questions. Thang 1 can also occur in conditionals. We can see the interaction between existence, negation, modality and mood in the occurrence of thang 1 in these six constructions and its positions in the hierarchical structure of functional categories. 2014 © 2014 The Author(s).