This paper argues that the best way of analyzing the directional morphemes in the Polynesian Outlier Vaeakau-Taumako (Pileni) is as verbs that most frequently—but not exclusively—occur in serialization with another verb. The class of directionals in Polynesian in general is somewhat heterogeneous; most sources classify them as particles or adverbs, while often noting that some items have a limited verbal use, or are homophonous with verbs with similar meanings.
The analysis of directionals as verbal in Vaeakau-Taumako suggests that they are less grammaticalized in this language than in most other Polynesian languages, and so raises the question of how this situation has arisen. One possible explanation is that the presence of verb serialization in Vaeakau-Taumako may have preserved the verbal nature of the directionals longer than in other Polynesian languages. This may in turn have been reinforced through contact with the neighboring Äiwoo language of the Reefs-Santa Cruz group, which has several serialization constructions that are structurally and functionally very similar to those found in Vaeakau-Taumako.
A second possibility is that the difference between Vaeakau-Taumako and other Polynesian languages is only apparent, and that Polynesian directionals in general may have verbal properties to a greater extent than generally recognized. As Polynesian languages are poor in verbal morphology, distinguishing verb serialization from other types of complex verbal constructions in these languages is problematic, which might explain why directionals have typically not been analyzed as verbal.