The study examines one component of the system of complementation in Palestinian Arabic. It is argued that the complementizer in question has an inherent semantics capable of influencing the meaning of sentences in which it is embedded. Specifically, its presence in a complex sentence communicates modal meanings distinct from those communicated by analogous sentences lacking it. This analysis challenges traditional assumptions about the functional importance of complementizers. It is hypothesized that the function of this complementizer is to lessen the degree of the matrix subject's commitment to the proposition embodied in the complement clause and to weaken the semantic and syntactic dependence of the clause. Examples are drawn from a number of complement clause types: with subjunctive and indicative complements, after perception verbs, and before direct quotations. Contains 10 references. (MSE)