Which That

Most grammarians have treated the word that , used in relative clauses, as a relative pronoun. However, its syntactic behavior is not at all like that of a pronoun, and therefore it must be a conjunction. Data from Standard English that -relatives and WH-relatives, non-Standard English that -relatives, and relative clauses in Dari (Kabul Persian) and Yoruba suggest that syntactic islands be added to the Keenan-Comrie Accessibility Hierarchy (1972). The use of that in relative clauses is related to its use as a complementizer with declarative verbs.