When you DO need a comma before "where":
* Introductory Phrases: When "where" introduces a dependent clause that comes before the independent clause, you usually need a comma.
* Example: Where the river meets the sea, there is a beautiful beach.
* Non-restrictive Clauses: When "where" introduces a clause that provides additional, non-essential information about a noun, you need a comma.
* Example: The restaurant, where we had our first date, is still there.
When you DON'T need a comma before "where":
* Restrictive Clauses: When "where" introduces a clause that is essential to understanding the meaning of the sentence, you don't need a comma.
* Example: The house where I grew up is now a museum. (This tells us which specific house is being referred to.)
* Prepositional Phrases: When "where" is part of a prepositional phrase that acts as an adjective, you don't need a comma.
* Example: I saw a bird where the trees were tallest.
Key Takeaway: The rule of thumb is to use a comma if the "where" clause can be removed without changing the basic meaning of the sentence. If the "where" clause is essential to understanding the sentence, no comma is needed.