Wiktionary
ergativity
n. (context linguistics English) A structuring property of the grammar of certain languages consisting in the differential treatment given to ''A'' (the subject of transitive verbs), in contrast to ''O'' (the object of transitive verbs) and ''S'' (the subject of intransitive verbs), which are treated similarly. This differential treatment may take the form of a special case marker (e.g., an affix or a particle) used with A but not with O or S, or of a specific agreement pattern (e.g., the verb may agree in person and number with A, but not with O and S).