This paper is about two syntactic relations formed between a phrase and a head merged as sisters to each other. Besides the canonical complementation, phrasal adjunction to a head is proposed as a licit syntactic relation. The head category projecting as a result of this relation is interpreted as a complex head in the semantic component, yielding complex predicate formation, in which the adjoined element modifies the content of the element that it adjoins to. In contrast to complementation, determined by both syntactic (like Case licensing) and semantic requirements (like selection), phrasal adjunction to a head is only triggered by a semantic requirement, i.e., predicate modification. Since this kind of adjunction does not fulfill any syntactic requirements, the movement of one element leaving the other in its base position is banned, resulting in strict syntactic unity. The motivation for this proposal mainly comes from light verb constructions in Turkish.