This paper analyzes a type of predicative structures belonging to a set of examples characteristically addressed in the literature on inarticulate constituents. Specifically, we focus on cases of completion (Bach, 1994; 2014), that is, sentences that express incomplete propositions or "propositional radicals", and that require additional and contextually recoverable propositional content. This type of expressions has been examined with regard to topics such as the underdetermination of meaning and implicit contents, central elements in the discussion about the syntax-pragmatics interface. We homogeneously analyze examples of completion as cases of adjunction, maintaining the separation between operations of argument licensing at a syntactic level, and other operations both semantically triggered and context-sensitive. In addition to the analysis of relational adjectives, our proposal extends to other types of incomplete propositions such as those expressed by predicates with missing objects or complements, superlatives, relational terms, taste predicates and dependent properties.