The active voice denotes that the subject is the agent of an action.
- Transitive: A transitive verb expresses an immediate impact on its object. The object is defined the accusative. Smyth 1705-1706
- Intransitive: An intransitive verb has an indirect impact on an object. The object can be 1) the subject, 2) defined by an oblique case, or 3) defined by a prepositional phrase. Smyth 1707-1710
The middle voice denotes that the subject is both an agent of an action and somehow concerned with the action.
The passive voice denotes that the subject is acted upon.