Why does only so and but have a comma in coordinating conjuctions?

It's not quite accurate to say that only "so" and "but" have a comma in coordinating conjunctions. The comma rule applies to all coordinating conjunctions when they join two independent clauses.

Here's a breakdown:

Coordinating Conjunctions: These words connect words, phrases, or clauses of equal grammatical rank. The most common ones are:

* For

* And

* Nor

* But

* Or

* Yet

* So

Independent Clauses: These are complete sentences that can stand alone. They have a subject and a verb.

The Comma Rule: When a coordinating conjunction joins two independent clauses, a comma goes before the conjunction.

Examples:

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

* Incorrect: I went to the store and I bought some milk.

Why is this rule important?

The comma helps the reader understand where one independent clause ends and the next begins. It avoids confusion and improves the clarity of the sentence.

Note:

* If the independent clauses are very short and closely related, the comma is sometimes optional (although it's always grammatically correct).

* When a coordinating conjunction connects items in a list or series, the comma is usually placed after the conjunction.

Let me know if you'd like to explore any specific example or have further questions.