Thursday, August 11, 2005

The two comma rules you need to know

Grammar is like golf, I tell people who ask me about getting better at it. You need to do it all the time. To be a good grammarian you have to work at it every day and practice it. If you don't, you'll lose it. In that way it is very different from riding a bike.

But memorizing the rules, keeping track of the guidelines, knowing the style preferences of whatever manual you choose to follow, is a daunting task for the average business writer. Heck, it's a daunting task for me, and I write every day.

So I try to boil down the most important grammar rules to the ones that will be needed the most by business writers. That way, today's multi-tasking workforce only has to be comfortable with Grammar's Greatest Hits list to make its writing as professional as it can be.

This post is about the rule on the top of the list. This rule will guide you to properly placing a good number of the commas you will use.

Correct comma use boils down to identifying essential and non-essential clauses. (Ring a grammar school bell?)

Knowing the difference is not really hard, especially with the memory tricks I'll share. And once you identify the different types of clauses, you will know exactly when to use a comma and when to leave it out.

Baby steps first. A clause is a group of related words that contains a subject (a noun) and a predicate, which is the part of the sentence that tells you what the subject does or what state of being the subject is in. In other words, it has a verb in it. It's a complicated definition for a very simple idea. It looks like this:

Stacy has handled the pressure of her new responsibilities well.

Stacy is the subject and has handled is the predicate. Got it?

Take another baby step forward.

An independent clause expresses a complete thought and can stand alone as a sentence. A dependent clause does not express a complete thought and cannot stand alone as a sentence. (I remember this by saying, "It is dependent on the rest of the sentence for meaning.")

Dependent clauses are the ones that have the comma rules tied to them for this post.

Okay, let's do essential clauses first.

An essential clause is a dependent clause that cannot be omitted from the sentence without changing the meaning of the main clause. Essential clauses ARE NOT set off by commas.


The magazine that came yesterday contains some stunning photographs.

How can you tell this is essential to the meaning? Take out that came yesterday and read the sentence again. What magazine are you referring to? There are lots of magazines on the table, so your meaning isn't clear. But adding the clause tells me which one you mean and is essential to my understanding your point.

Here's the memory trick:

Think of commas as tourniquets--adding them here would cut off the supply of crucial information to the rest of the sentence, just like blood flow would be cut off to an appendage.

Hey, I watch ER, so you'll have to forgive the gore.

So what about non-essential clauses?

This is a dependent clause that adds descriptive information but could be omitted without changing the meaning of the main clause. Nonessential clauses ARE set off by commas.


Her latest CD, which is an artistic departure, hit the charts in the Top 10.

The dependent clause here is added information. I know which CD the writer means because of the word "latest" in the sentence. So it's not essential to the meaning.

The tourniquet analogy will help you to remember this rule here. We can cut off this information with commas (word tourniquets) because it's not vital to keeping the main message alive. The main clause doesn't need the oxygenated blood supply to keep it alive. So this clause could wither and die.

This is a hard-and-fast rule and no one can argue the commas you use in these instances. There are subjective comma usage issues which cause lots of arguments, and I'll post about those in the future.

If you're looking for a good resource to all things grammar, go get a Gregg Reference Manual. I've had one since college and I wouldn't write from home without it. You'll have all the rules and definitions within an arm's reach.

But for now, become dependent on the tourniquet analogy because it's essential to you using commas correctly, which no one should call a non-essential skill. At least, not in my book.