Semantic Roles

Abstract

The meaning of a predicate, especially a verb, may be characterized via the relations that its arguments bear to it. Semantic roles—also known as thematic relations, theta roles, participant roles, and deep cases—are labels for certain recurring predicate-argument relations. They have proved attractive because they provide a way of representing commonalities across different uses of the same predicate or across uses of distinct but semantically related predicates that may be obscured because arguments with certain semantic roles may have various syntactic realizations. Thus they provide a level of abstraction for the statement of generalizations concerning a variety of linguistic phenomena. In particular, argument realization generalizations are often stated over a thematic hierarchy, a ranking of semantic roles. However, semantic roles have not lived up to their initial promise. It has proved impossible to find a small set of roles that can be applied across all verbs in a language, let alone across languages. Yet this desideratum must be met if semantic roles are to figure effectively in accounts of linguistic phenomena. Further, some generalizations involving semantic roles seem to require reference to coarse-grained roles, whereas others require reference to fine-grained roles. Moreover, reliable diagnostics are difficult to identify even for the roles cited most often. Although these difficulties have led some researchers to reject semantic roles, others have taken alternative approaches, including the use of generalized semantic roles, which are inspired by the notion of prototype, with no single property being necessary or sufficient for an argument to bear such a role. Despite these drawbacks, semantic roles continue to be useful in stating linguistic generalizations, and so descriptive, if not theoretical, uses of semantic role labels persist across subfields, including language acquisition, psycholinguistics, and neurolinguistics. Furthermore, semantic roles are useful in natural language processing. Since semantic roles have been implicated in phenomena involving argument structure, the separate Oxford Bibliographies article Argument Structure should be consulted for additional relevant resources. Acknowledgments: For discussion of the material in this article, the author is grateful to Scott Grimm, Chris Manning, Malka Rappaport Hovav, and two reviewers, as well as the students in her autumn 2012 lexical semantics class.