Non-restrictive clause: A non-restrictive clause provides additional information that is not essential to the meaning of the sentence. It can be removed without changing the basic meaning of the sentence.
Examples:
* The dog, which was very playful, chased its tail. (The clause "which was very playful" is non-restrictive. We know the dog is being discussed, so the clause provides extra information.)
* My car, which is red, needs a wash. (The clause "which is red" is non-restrictive. We already know which car is being discussed.)
Restrictive clause: A restrictive clause is essential to the meaning of the sentence. It cannot be removed without changing the meaning of the sentence.
Example:
* The dog which was chasing its tail ran into the street. (The clause "which was chasing its tail" is restrictive because it tells us which specific dog is being discussed.)
In this example, we need the clause to understand which dog ran into the street.
Here's a simple way to remember:
* Non-restrictive clause: Comma before "which"
* Restrictive clause: No comma before "which"