Recent work on the typology of parts-of-speech systems has shown that a significant parameter of variation in the organization of the lexicon concerns the number of open or major word classes that are recognized in a language. While languages with the familiar Indo-European system distinguish four major "contentive" classes (noun, verb, adjective, and adverb), it is not uncommon for languages to distinguish fewer. In many such cases, a language with a reduced parts-of-speech inventory conflates two or more major classes, creating a flexible part of speech that fills a variety of syntactic roles. One of the most contentious issues that falls out from this observation is whether or not it is possible for a language to conflate all of the major lexical classes, grouping all of its contentive lexical items into a single, maximally flexible class of words (opposed only by the minor, grammatical classes) and thereby neutralizing the distinction between nouns and verbs. Claims for the absence of a noun-verb distinction have been advanced for a number of languages and are discussed most extensively for languages from the Salishan, Polynesian, and Munda families. Examining these cases reveals that they fall into two general types which I will refer to in this paper, loosely following Evans and Osada (2005), as precategorial and omnipredicative. The precategorial type of language, as represented by languages of the Munda and Polynesian families, has received the most attention in the recent literature (e.g., Broschart 1991; Croft 2000; Vonen 2000; Hengeveld and Rijkhoff 2005); the omnipredicative type has not been discussed to the same extent, although languages of this kind, particularly those belonging to the Salishan family, are frequently offered uncritically as examples of languages that lack a distinction between nouns and verbs.In this paper, I will present data from the Salishan language Lushootseed 1 which demonstrates 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 that will be referred to here as unidirectional flexibility. Unidirectional flexibility as the term is used here is intended to complement the notion of "bidirectional flexibility" put forward by Evans and Osada (2005) as a criterion for determining whether or not a language has genuinely neutralized a part-of-speech distinction. For Evans and Osada, a particular part of speech is considered to be bidirectionally flexible if all of its members can occupy the syntactic * The author would like to thank Paulette Levy and Igor Mel'čuk for helping him refine the ideas behind this paper, as well as Jan Rijkhoff, Eva van Lier, and three anonymous reviewers for their helpful critiques and suggestions. My thanks also to the late Thom Hess for providing me with the data and understanding of Lushootseed that lie behind this paper. None of the above bear any responsibility for my errors. 1 Lushootseed is a member of the Central Coast Salish branc...