Published online by Cambridge University Press: 27 June 2016
Ergativity is a term used in traditional descriptive and typological linguistics to refer to a system of nominal case-marking where the subject of an intransitive verb has the same morphological marker as a direct object, and a different morphological marker from the subject of a transitive verb. Languages in which this system is found are divided into two main types, A and B (following Trask 1979:388). In Type A the ergative construction is used equally in all tenses and aspects. Furthermore, if there is verbal agreement, the verb agrees with the direct object in person and number in exactly the same way it agrees with the subject of an intransitive verb. The verb agrees with the transitive subject in a different way. Well-known representatives of this type are Basque, Australian ergative languages, certain North American languages, Tibeto-Burman and Chukchee. In type B there is most often a tense/aspect split, in which case the ergative construction is confined to the perfective aspect (or the past tense), and the nominative-accusative configuration is used elsewhere. Furthermore, if there is verbal agreement, the verb may agree with the direct object in number and gender but not in person.