Ergative case
In grammar, the ergative case (abbreviated erg) is the grammatical case that identifies a nominal phrase as the agent of a transitive verb in ergative–absolutive languages.
Ergative–absolutive alignment contrasts with nominative–accusative alignment in which subjects of transitive and intransitive sentences behave similarly, and differently from objects of transitive sentences. For example, a sentence like "I help him" has "him" as the object and "he sleeps" has "he" as the subject. But in languages that have ergative-absolutive alignment, the ergative case is used as the subject only in a transitive sentence, otherwise the absolutive case is used. An analogue in English would be saying "I help him" and "him sleeps."