The passive voice describes a sentence that has no explicit subject. English represents the passive voice with verbal constructs like “the pillar was broken”, leaving the person doing the breaking unspecified. Tolkien said that in Adûnaic, the passive voice was rendered by “impersonal verb forms” (SD/439). Andreas Moehn suggested (LGtAG) that such verbs would simply omit any subject or pronominal-prefix.

Tolkien also cryptically indicated the passive voice had “the subject in accusative” (SD/439), but Adûnaic has no accusative case. Perhaps he meant the “subject” of the English construction (really the object of the verb) was put into the object position in Adûnaic. If so, the sentence “the pillar was broken” might be rendered in Adûnaic as the subject-less sentence rahhata târik “[...] did break the pillar”.