Passive voice

Passive voice is a grammatical construction that changes how an event's participants are expressed, typically placing an affected participant in the subject relation while omitting the actor or expressing it differently. It belongs to grammatical voice, not simply to a choice of slow or indirect wording.^[ref]

Compare The mechanic repaired the pump with The pump was repaired by the mechanic. Both can describe the same repair, but the pump changes from object to subject; the mechanic is expressed in a separate phrase. Omitting that phrase gives The pump was repaired without specifying who performed the repair.

This is useful for separating thematic roles from grammatical relationships. A representation that treats every subject as the actor will misdescribe the passive example. The Universal Dependencies label nsubj:pass preserves subject status while recording the passive construction, making the analysis inspectable in a text corpus.