Previous work in syntax, semantics, pragmatics, and psycholinguistics has shown adjectives to take an intermediate position between nouns and verbs. This claim is made more specific in this article through a phonological (and to a lesser extent, morphological) test of the ‘equidistance hypothesis’. On seven criteria, English adjectives are found to exhibit a much greater affinity with nouns than with verbs. This pattern of results is brought about by the syntagmatic context in which the three word classes typically occur. The rhythmic context in which adjectives are embedded is similar to that of nouns but dissimilar to that of verbs. This bias gives rise to suprasegmental differences which in turn lead to segmental differences. The proposed account rests upon the assumption, independently verified, that nouns and verbs differ in length, a disparity that might have a syntactic cause. A tentative case is made for a cross-level harmony constraint according to which the similarity between adjectives and nouns is not particular to the phonological level but characterizes the linguistic system more generally.