Noun
ergativity (uncountable)
(linguistics) The property of a grammar's (or, by extension, a language's) being ergative; the attribute of possessing a grammatical pattern such that the object of a transitive verb is treated the same way as the subject of an intransitive one, while the subject of the transitive verb is treated differently.
Ergativity entails that the grammar give treatment to the subject (A) of a transitive verb that is differentiated from the treatment given to the object (O) of such a verb and the subject (S) of an intransitive verb, which are treated similarly to each other. Such differential treatment may take the form of a special case marker (such as an affix or a particle) used with A but not with O or S, or of a specific agreement pattern (for example, the verb may agree in person and number with A, but not with O and S).