When do you use a comma in compound sentence?

You use a comma in a compound sentence when you have two independent clauses joined by a coordinating conjunction. Here's a breakdown:

1. Independent Clauses:

* An independent clause is a group of words that can stand alone as a complete sentence. It has a subject and a verb and expresses a complete thought.

* Example: The cat sat on the mat.

2. Coordinating Conjunctions:

* These are words that connect two equal parts of a sentence. The most common ones are:

* For

* And

* Nor

* But

* Or

* Yet

* So

* Example: The cat sat on the mat, and it purred loudly.

3. Putting it Together:

* A compound sentence is formed when you connect two independent clauses with a coordinating conjunction.

* You use a comma before the coordinating conjunction to separate the two clauses.

Here are some examples:

* Correct: The sun was shining, but the wind was cold.

* Incorrect: The sun was shining but the wind was cold. (No comma before "but")

Important Note: There are a few exceptions to this rule, such as when the clauses are very short or when the sentence is very simple. However, using a comma is generally the safest option.