Like the Martha Stewarts of grammar, commas keep your sentences organized. Sometimes commas are optional, but there are times when you must use them or risk looking ignorant or gauche. So dust off your tux, straighten your moustache, and follow me into the Casino Royale of comma rules.
Commas and Conjunctions: Like Pancakes and Maple Syrup
Use a comma before a conjunction. What’s a conjunction? It’s a word like and, but, or yet that joins two sections of a sentence the way a hitch joins two train cars.
- I’ve trained the squirrels outside my window to do back flips and pyramids, and we’ll be taking our act on the road next week.
- He bought the jester’s costume and the floppy hat, but I can’t help feeling his heart isn’t in it.
If a sentence is short and its parts are closely related, you can leave out the comma:
- I dropped her off at the racetrack and I haven’t seen her since.
Whatever you do, don’t stick a comma in your sentence instead of a conjunction. It simply can’t take the weight, and your sentence will go off the rails:
- I’m going as a cephalopod, I’ve already bought the suction cups.
The above comma needs to be either helped by a conjunction or replaced by a semicolon, which is stronger than a comma:
- I’m going as a cephalopod, and I’ve already bought the suction cups.
- I’m going as a cephalopod; I’ve already bought the suction cups.
Or if you’re a Hemingway-esque writer who likes ’em short and choppy, you can divide your sentence into two:
- I’m going as a cephalopod. I’ve already bought the suction cups.
Try not to get overexcited and slap a comma in front of every and or but you see. Conjunctions can be sneaky, and sometimes you’ll find them playing different roles. They don’t need commas when they’re not acting as hitches. Consider the following sentence:
- I wanted to go to the orgy but couldn’t find any whipping cream.
The second train car (“couldn’t find any whipping cream”) doesn’t have a subject—without the first car we don’t know who was at a loss for dairy products. The I from the first part is doing double duty for both verbs, wanted and couldn’t, which makes this one train car, not two (or a compound predicate if you want to get technical).
- I wanted to go to the orgy, but I couldn’t find any whipping cream.
In this case we have two subjects and two verbs, which means we have two train cars (or independent clauses) joined by a hitch. As such, this but can take a comma (although the sentence is short enough to go without one if you wish).
Lists: Keeping Things in Line
When your sentence has a list of three or more, use commas to keep them separated and avoid fights:
- According to The Hitchhiker’s Guide to the Galaxy, the ingredients for a Pan Galactic Gargle Blaster include Ol’ Janx Spirit, seawater from Santraginus V, Arcturan mega-gin, Fallian marsh gas, Qualactin hypermint extract, the tooth of an Algolian suntiger, zamphour, and an olive.
- A mouse, a duck, a dodo, a lory, an eaglet, and several other curious creatures ended up in the pool of tears with Alice.
You’ll notice both these sentences have a comma before the final and. This is called a serial comma (like a serial killer, only nicer) and it is completely optional. Whether you decide to use it or not use it, be consistent. Dropping or adding it halfway through your writing makes you look either sloppy or just plain confused.
Grammar’s Romeo and Juliet
Avoid the mysteriously common error of putting a comma between the subject and the verb:
- People who live in glass houses, shouldn’t clean in the buff.
The subject (people) and verb (shouldn’t) are like lovers who long to be together. It would be wrong to come between them.
- People who live in glass houses shouldn’t clean in the buff.
Next week: sideshow commas, the that/which rule, vampires, and go-go dancers.