Do you use a comma before the word and?

In most cases, you should use a comma before the word and when it joins two independent clauses. An independent clause is a group of words that contains a subject and a verb and can stand alone as a sentence.

For example:

* I went to the store, and I bought some milk.

* The sky is blue, and the grass is green.

* The dog barked, and the cat ran away.

However, there are some exceptions to this rule. You should not use a comma before and if:

* The two clauses are joined by a coordinating conjunction other than and, such as but, so, or or.

* The two clauses are very short.

* The second clause is a very close restatement of the first.

For example:

* I went to the store but forgot to buy milk.

* The sky is blue and the grass is green.

* The dog barked and ran away.

If you are not sure whether or not to use a comma before and, it is best to err on the side of caution and use the comma.