Lately, I've noticed a few different species of comma users. It interesting to see the way people misuse them. Let's take a look at some of the groups of comma abusers that you might encounter in the wild:
1. Overusers - This group is probably the largest group of comma abusers in existence. They sprinkle extra commas everywhere. When in doubt, they always drop in an extra comma.
2. Abstainers - This group shuns commas entirely. Their motto seems to be: when in doubt, leave it out. Also, when you're sure, leave it out. It is a bit jarring to see an appositive phrase naked against the word it modifies.
3. Guessers - These people are very inconsistent in their comma use. They can't quite remember the rules. Each sentence is a new adventure with them.
4. Conjunctioners - This is a rare species of comma abusers. A conjunctioner will isolate each and every conjunction in a sentence with commas. (We'll look at this below)
So, when should one actually use a comma? Let's look at the most obvious cases and keep things simple.
When to use a comma:
1. To indicate a pause - This is the raison d'etre of a comma. Anytime you want to indicate a slight pause, use a comma. For a full stop, use a period.
2. To directly address someone or something - Use a comma before the person or thing being addressed. (see the post "Goodbye, Vocative" for a more detailed explanation).
3. Before a negating conjunction - Do not use a comma with "and" or "or". Use a comma with "but", which indicates a negation or exception to the previous clause.
4. Before a modifier - The "which" in the previous sentence is a good example. It introduces a modifier (in this case, a clause). For an appositive phrase (another type of modifier), use a comma both before and after the phrase. Look at the following sentence. Jane's friend, Billy, eats marshmallows. "Billy" is the appositive phrase.
5. Before a verb in the present progressive - A verb in the present progressive ends in "-ing". This is sometimes incorrectly called the "gerund", but a gerund indicates a nominal form (not a verbal form). An example of this usage might be: Susan walked into the room, eating a handful of popcorn.