I fully understand the annoyance people have with commas. I also understand that there is a lot to know about linguistic constructs (i.e. - how to put a sentence together) that a lot of writers don't have a firm grasp on. That's why there are editors like me.

There are a lot of uses for a comma. Some of the ones listed on Wikipedia's entry (and the most common ones that writers would use) are these:

1. Introductory words and phrases
2. Parenthetical phrases
3. Separation of independent clauses with a coordinating conjunction
4. Separation of initial dependent clause from independent clause
5. Separation of items in a list or coordinating adjectives

Those three bold items are the most important ones. They're the ones people mess up on the most. I'll detail them below.

The most important part of commas is the distinction between independent and dependent clauses. An independent clause is – in short – a sentence. It is a clause that can stand on its own with an action and an actor (a subject and a verb - John ran). A dependent clause is a clause or phrase that cannot function on its own because it has a)either no verb or no subject, b)is begun with a subordinating conjunction, or c)is introduced with a preposition. For example:

• a) *John's apartment (no verb)
• b) *Because Lucy is out of town (subordinating conjunction)
• c) *If John is sick (prepositional phrase)

Commas are tricky for a lot people. The biggest mistake is the overuse of them. Many writers unfamiliar with their grammatical use or purpose often stick them in anytime a “pause” is sensed in the writing. This is not only incorrect, but it's a dangerous use of language, because many times it confuses the writing and the reader.

I'll go into more later in this set of posts, but one trick to help alleviate the overuse of commas is to learn a bit more about the function of colons and semi-colons. Both of these are wonderful tools for writers (primarily fiction writers) and can really give some variety to your language. As a general rule (when it comes to editors), learn at least the basics of comma use from a grammar book. Or you can always look it up online. Grammar Girl has some good uses of commas, too.

So back to the examples.

Parenthetical Phrases - They don't have to be in parenthesis.

John, who lives down the street, loaned me his guitar.

“John loaned me his guitar” is the complete sentence. The bit in the middle “*who lives down the street” is an incomplete sentence (it begins with a subordinating pronoun) and is additional information for the sentence.

Separation of independent clauses with a coordinating conjunction

Marcus loves the zoo, so he goes every week.

Two complete, independent clauses (sentences). “Marcus loves the zoo” and “he goes every week”. The comma + 'so' is a coordinating conjunction linking the two.

Separation of initial dependent clause from independent clause

Whenever I get angry, I go for a walk.

Two parts to this sentence: “*Whenever I get angry,” and “I go for a walk.” “I go for a walk” is an obvious sentence. “*Whenever I get angry” is not. It is made dependent because of the conjunction 'whenever'.

That's the not-so-short and not-so-skinny about commas. If you have questions, send them to me.

Table of Contents:

1. Grammar. Yes. Grammar: An introductory post on the series

2. That's It. Period: A post on the full stop.
3. OMG! What's the Deal?: A post on question marks and exclamation points.
4. You Say Potato; I Say Potato: A post on semi-colons.