Valency theory is a grammatical theory which focuses on the verb or the predicate as its center. Modern valency theory was founded in 1959 by Lucien Tesnière and is based on the idea that verbs structure sentences by binding specific elements (complements, actants) as atoms do. Other, freely addable elements are not determined by the verb; these are called supplements, adjuncts, or circonstants. The basic items of valency theory are valency carriers, complements, and supplements. Take for example sentence (1), “He gives the book to Sandra in the library.” While the NPs He and the book and the PP to Sandra in sentence (1) are valency governed complements, the PP in the library is not governed. It is a supplement. Tesnière compares sentences to a stage play, with actors and requisites. The verb is considered the central valency carrier and the complements depend on the valency carrier. In contrast to other projective theories of grammar, such as generative grammar, the binary division of the sentence into subject and predicate is abolished: the prime element of a sentence is the verb, the subject is governed by the verb, and so are the other objects. In valency theory the number of complements that depend on the verb constitutes its valency. There are monovalent (run), bivalent (build), and trivalent verbs (give). The verb run requires a subject to form a minimal sentence and to communicate a scenario, build requires a subject and direct object for this purpose, give a subject, direct, and indirect object. But it is not necessary that every complement be realized. For instance, sentence (2): “He sold the car (to his neighbor)”. A trivalent verb like to sell can easily be realized with only two complements, as shown in example (2). Complements like the directive complement in (2) (called facultative complements) and supplements differ by the fact that complements are determined in their form (syntactic valency) and their meaning (semantic valency) by the valency carrier, while supplements such as temporal or local adjuncts are not. The ability of a valency carrier to determine formal aspects like case marking of its complement(s) is subsumed under syntactic valency and the ability to determine semantic aspects like its thematic role is called semantic valency/specificity. Acknowledgements: For discussion of the material in this article and notes, the author is grateful to Vilmos Ágel, Klaus Fischer, and the reviewers.
Valency Theory