In this paper we intend to show that Mundari is one of the languages without distinct classes of verbs and nouns as far as its basic, non-derived vocabulary is concerned. Our contribution is organized as follows. Section 2 briefly presents a typology of parts-of-speech (PoS) systems, followed by a critical evaluation of the three criteria Evans & Osada (E&O - this volume) use to establish the lack of word class distinctions in a language (section 3). In section 4 we present evidence to support our claim that Mundari has ‘flexible’ basic lexemes (i.e. there is no fundamental distinction between nouns and verbs), thus disputing E&O’s claim that Mundari has clearly definable classes of verbs and nouns. The last section is concerned with a set of grammatical features which correlate with the presence of flexible lexemes in a language. It is concluded that Mundari displays all of the predicted features of a language that does not clearly distinguish between separate classes of nouns and verbs.