 Subject (grammar)

A subject is a grammatical relation identified through language-specific structural tests, such as word order and grammatical agreement. It often corresponds to the actor in a simple active clause, but that semantic association is not its definition. A noun phrase can be a subject without describing an intentional action.^[ref]

Compare A gust broke the branch and The branch was broken by a gust. The first has a gust as its subject; in the passive voice version, the branch has that relation. The participants' involvement in the event has not simply exchanged places. Separating grammatical relations from thematic roles explains the contrast.

In Universal Dependencies, a nominal passive subject can receive nsubj:pass, explicitly preserving its subject status. Such a representation supports a testable structural account and prevents a procedure from assigning “subject” solely to whichever expression appears to name a doer.