This paper presents a semantic characterization of two kinds of nominalizations in Turkish that can appear as complements to predicates, namely -MA and -DIK nominalizations. I propose that these nominalizations denote predicates of events and propositions, respectively. I show that a number of reportedly syntactic contrasts between these two nominalization types follow from this semantic characterization. Notably, the proposed semantic types correctly predict the flexibility of -MA nominalizations. Unlike -DIK nominalizations, they can appear as definite or quantified event descriptions, or propositional attitudes. This characterization makes more fine-grained predictions on when the reported contrasts between the nominalizations can be detected, and more generally brings in empirical support for the entity-event uniformity in the domains of plurality and quantification.