This paper focuses on relational adjectives (AREL) that modify deverbal nouns. It aims to demonstrate that the argumental (or thematic) relationships expressed by these adjectives vary and that they are dependent not only on the N-AREL link but also on the discourse context and on speakers’ general knowledge. We compare the encoding of an argument as an adjective and as a prepositional phrase. It is argued that the difference between classifying and thematic adjectives (Bosque 1993) is blurred in usage, as classifying readings that establish oppositionally-organized fields of application of the N are also attributed to argumental adjectives. It is thought that the relevant factor of this superposition is that the only formal marking of the N-AREL relation is the postposition, and that this mark signals a contrastive characterization, that is, a characterization that establishes differences (Klein-Andreu 1983).