A case for marking the subject of transitive verbs only. The intransitive subject and the direct object are marked with another case, called absolutive or nominative. This is in contrast to the system familiar to European speakers where the transitive and intransitive subjects share the nominative case, and the direct object is distinguished with the accusative. Although only Basque is ergative in Europe, the system is common and applies to about 30% of the world's languages.

Before it was appreciated how common it was, the few ergative languages known were mis-analysed as "passive", because an active ergative sentence looks rather like the passive voice. But the ergative subject is the subject and comes first. It's not a passive agent shunted off into an oblique case.