Here's why:
* Connects Clauses: It joins a dependent clause (the one starting with "when") to an independent clause.
* Shows Time Relation: It indicates the time at which something happens.
Example:
* When the bell rings, we will go to lunch. ("When the bell rings" is the dependent clause, and "we will go to lunch" is the independent clause.)
Let me know if you'd like to explore other examples or parts of speech!