* Subordinating Conjunction: This is the most common use of "when." It connects a dependent clause to an independent clause, showing the time relationship between the two.
* Example: *I will go to the store when I finish my homework.*
* Adverb: "When" can act as an adverb, modifying a verb, adjective, or another adverb. It answers the question "When?"
* Example: *I went to the store when it was raining.*
* Interrogative Adverb: "When" can introduce a question about time.
* Example: * When did you finish your homework?*
So, the specific grammar classification of "when" depends on its context in the sentence.