nullsubject

Null subject refers to the absence of an overt subject pronoun in a finite clause, a phenomenon found in many languages where verb morphology encodes person and number. In pro-drop languages, the subject is not required to be overt because the verb form provides sufficient person and number information, and the subject can be recovered from context or discourse. In some syntactic analyses, the missing subject is represented by a silent category (often called PRO) or by zero agreement between the verb and an implied subject.

Languages with strong pro-drop properties include most Romance languages (Spanish, Italian, Portuguese, Romanian), Greek, and several Slavic languages (such as Bulgarian). East Asian languages like Japanese and Korean are also routinely pro-drop, dropping subjects and even objects in contexts where they are recoverable. By contrast, English and German typically require overt subjects in finite clauses, although imperatives in English allow a vocative-like form with an implicit second-person subject.

The distribution of null subjects is a major topic in syntactic typology and is captured by the Null Subject Parameter, a proposed grammatical parameter distinguishing pro-drop from non-pro-drop languages. In syntax, the null subject status interacts with subject-verb agreement, verb morphology, and discourse context. For language learners and natural language processing, identifying when a subject may be omitted depends on language-specific morphology and discourse cues, and on the syntactic rules governing topic, focus, and agreement.

See also: pro-drop, zero pronoun, subject ellipsis.