Reduced relative clause

A reduced relative clause is a relative clause that is not marked by an explicit relative pronoun or complementizer such as who, which or that. An example: the clause I saw in the English sentence "This is the man I saw." (Unreduced forms of this relative clause would be "This is the man that I saw" or "...whom I saw". The form "...who I saw" is technically ungrammatical because the relative pronoun must take the case of the substantive to which it refers.)

Another form of reduced relative clause is the "reduced object passive relative clause", a type of nonfinite clause headed by a past participle, such as the clause found here in: "The animals found here can be dangerous."

Reduced relative clauses are given to ambiguity or garden path effects, and have been a common topic of psycholinguistic study, especially in the field of sentence processing.

Regular relative clauses are a class of dependent clause (or "subordinate clause") that usually modify a noun. They are typically introduced by one of the relative pronouns who, whom, whose, what, or which—and, in English, by the word that, which may be analyzed either as a relative pronoun or as a relativizer (complementizer); see That a relativizer.

Reduced relative clauses have no such relative pronoun or complementizer introducing them. The example below contrasts an English non-reduced relative clause and reduced relative clause.

Because of the omission of function words, the use of reduced relative clauses, particularly when nested, can give rise to sentences which, while theoretically correct grammatically, are not readily parsed by listeners. A well-known example put forward by linguists is "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo", which contains the reduced relative clause Buffalo buffalo buffalo (meaning "which buffalo from Buffalo (do) buffalo").

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