The interplay of nominality and adverbiality in Phola

Some Yi/Ngwi languages exhibit functionally versatile word classes, including nouns which can be used as both referential arguments and adjuncts, covering functions typically associated with adverbs. As a result, adverbs are often treated as a residual word class in the literature on these languages. This article aims to complement the picture of adverbiality in this subbranch of Tibeto-Burman by offering novel data on Phola, a Yi/Ngwi language of Yunnan. It is shown how adverbial expressions of time, space and manner exhibit unique constructional properties, which set them apart from nominal expressions. Very particularly, Phola adverbial expressions, in contradistinction to canonical nouns, must be relativised before they can be used as noun-modifiers. This suggests they are underlyingly part of the verb phrase, a property that lexical adverbs exhibit in languages where their existence as a word class is uncontroversial. The Phola facts are compared to those of other Ngwi languages, especially Lahu, the single best described Ngwi language, where adverbial expressions are largely found to be constructionally identical with canonical nouns. The differences between such two closely related languages highlight the need for a stronger focus on language-internal distributional criteria when addressing the thorny task of defining and assigning word classes.