Clauses usually orient around something the rest of the clause is about. The subject is the grammatical relation prototypically associated with the actor or topic of a clause and controlling agreement on the verb in many languages.

Subjects often appear before the verb in declarative sentences of subject-verb-object languages, but order is not a universal definition. Case marking, agreement, and syntactic tests identify subjects more reliably than meaning alone. Dummy subjects fill the slot when no semantic argument is available.

Subjecthood plays a major role in typology, acquisition, and parsing. Passive voice rearranges which participant appears as subject without changing underlying event participants. Teaching materials introduce subjects early because they anchor basic sentence patterns.

• Core grammatical relation in a clause
• Often controls verb agreement
• Prototypically the actor or topic
• Identified by structural tests, not meaning alone