Split ergativity is shown by languages that have a partly ergative behaviour, but employ another syntax or morphology (usually accusative) in some contexts. In fact, most of the so-called ergative languages are not pure but split-ergative.
The split is usually conditioned by one of these:
- The presence of a discourse participant (a first or second person) in the proposition. The Australian language Dyirbal behaves ergatively in all morphosyntactic contexts, except when one of these is involved. When a first or second person pronoun appears, however, it is marked according to a nominative-accusative pattern (with the least marked case when it is the subject, and with the most marked case when it is the object).
- The use of certain tenses and/or aspects in the verb. The Indo-Iranian family, for example, shows a split between the perfect and the imperfect aspect. A verb in the perfect aspect causes its arguments to be marked using an ergative pattern, while the imperfect aspect triggers accusative marking. (Related languages and others always tend to associate past tense and/or perfect aspect with ergativity.)