The word "that" is a pronoun and a subordinating conjunction used in English. It serves multiple roles. As a pronoun, it can refer to a specific person, thing, or idea. As a conjunction, it introduces a dependent clause, connecting it to an independent clause. It is often used to specify or identify something, providing clarity in communication.
The word "that" originates from Old English "ðæt," which is a demonstrative pronoun. It has akin roots in other Germanic languages, reflecting its longstanding use in the English language structure.