Language universals and linguistic variation are important concepts underlying all syntactic theories. In this paper, we aim to show how these two notions are illustrated in the construct of optimality theory (OT). To achieve this goal, we present a case study that involves three Austronesian languages, Tagalog, Atayal, and Tsou, to help demonstrate that OT is an appropriate syntactic theory to deal with the inherent conflict of the two notions. As will be shown, the three languages exhibit different ordering of precedence between the head noun and two types of relative clauses. An OT approach allows us to adopt the same syntactic schema and the same syntactic constraints to account for the cross-linguistic ordering variations. The different hierarchical ranking proposed for the same set of constraints successfully established a syntactic pattern that shows universal properties on the one hand, and allows linguistic variation on the other.
