Answer:
relative pronoun, subordinate conjunction
Explanation:
Relative pronouns like who, whom, which, or that are most often used to introduce subordinate clauses, e.g. "The electric guitar that my brother bought me is awesome." The underlined portion is the subordinate clause, introduced by that, modifying the subject in the main sentence "The electric guitar." The same is true for subordinate conjunctions like after, because and until: "I will be waiting here until you decide to return." Once again, the result is a clause (subject you + predicate decide to return) that, due to the subordinating conjunction, cannot stand on its own as a sentence.
