Answer:
Relative pronouns.
Explanation:
Relative pronouns are words used to combine two clauses into one.
The cashier who began working today rang up the manager's order.
A relative clause is a dependent clause that modifies a noun. It is introduced by a relative pronoun or a relative adverb.
The dependent clause who began working today modifies a noun, cashier. It is introduced by a relative pronoun, who.
