Here's why:
* Relative pronouns connect a dependent clause to an independent clause and refer to a noun in the main clause. Examples include "who," "which," "that," "whom," and "whose."
* "Although" is a subordinating conjunction. It introduces a dependent clause that expresses a contrast or concession.
Example:
* Relative pronoun: "The book that I read was interesting." ("That" refers to "book.")
* Subordinating conjunction: "Although it was raining, we went for a walk." ("Although" introduces a contrasting clause.)
In short, "although" doesn't act as a pronoun or refer to a noun. It connects clauses by showing a contrasting relationship.