How does ergativity work in Tibetan and other Tibeto-Burman languages?

In many Tibeto-Burman languages, including Tibetan, Newari, and Akha, ergativity is a key grammatical feature.1

In these languages, ergativity functions by treating the subject of an intransitive verb the same way as the object of a transitive verb. This contrasts with nominative-accusative languages, which group the subjects of both transitive and intransitive verbs together while distinguishing them from the object of a transitive verb. In the context of Tibeto-Burman grammar, agents are typically marked similarly to instrumentals.12

Some languages within this family exhibit "split ergativity," such as Limbu and Sherpa. In these systems, ergativity is not applied universally but is restricted to specific tenses or aspects, such as appearing only in the past tense or the completive aspect.1

It is important to note that the traditional notions of "subject" and "object" are often considered alien to the underlying structure of Tibeto-Burman grammar, which is frequently topic-prominent and relies on different mechanisms to express grammatical relationships.1