This book offers a fresh perspective on how natural languages encode grammatical relations, by delving into the interplay between oblique cases, adpositions, serial verbs, and applicatives. This book reveals, through a series of case studies, the pervasive role of the 'inclusion' relator across diverse linguistic contexts. Departing from traditional views that obliques lack interpretive content, this work presents a unified conceptual framework of relations in grammar. Drawing on minimalist principles, the book posits a preeminence of the lexicon in syntactic projection, shedding light on the underlying ontology of language. By exploring cross-categorial variation and syncretism, it outlines an inventory of primitives shaping morpho-syntactic derivations.