Unidirectional flexibility and the noun–verb distinction in Lushootseed1

One of the most contentious issues in the typology of parts-of-speech systems is whether it is possible for a language to neutralize the distinction between nouns and verbs. Languages of the Salishan family are often cited as languages that exhibit this kind of neutralization. In this chapter, Beck presents data from the Salishan language Lushootseed which demonstrate that, while the noun–verb distinction is neutralized in syntactic predicate position, it is still relevant for words used as syntactic arguments, giving us a pattern referred to here as unidirectional flexibility. While unidirectional flexibility entails the neutralization of a parts-of-speech distinction in a particular syntactic environment, it cannot be equated with the complete absence of the distinction. The same line of reasoning can be fruitfully applied to other languages, such as Tongan, which have also been claimed not to distinguish nominal and verbal categories.