The issue of lexical flexibility is best tackled as the articulation of two separate mappings: one that assigns lexical items to word classes; another one that associates these word classes with the syntactic functions they can access. A language may endow its lexemes with more or less multicategoriality, and its word classes with more or less multifunctionality: these are two distinct facets of lexical flexibility, which should be assessed separately. Focusing on Hiw, an Oceanic language of northern Vanuatu, I show that lexical flexibility is there mostly due to the high multifunctionality of its word classes, each of which can regularly access a broad array of syntactic functions. Conversely, Hiw ranks relatively low on the scale of multicategoriality: most of its lexemes are assigned just one word class. This is how a language can be grammatically flexible, yet lexically rigid.