“I’m the comma queen! Help me! I need to know when to stop!” So pleaded a friend of mine this week. So, for the benefit of all my comma-happy readers, allow me to present . . .
The Four Basic Occasions to Use a Comma.
1) To separate items in a series. This one I think we’re all familiar with:
I had pancakes, eggs, bacon, and toast for breakfast this morning.
OR I had pancakes, eggs, bacon and toast for breakfast this morning.
(Note: That comma before the “and” is called the Oxford Comma, and it is optional. I almost always use it because there are times when it is necessary for clarity, so I just make it a habit.)
2) To set off introductory elements in a sentence. This could be a word, a phrase, or a whole clause – anything that comes before the main independent clause of a sentence:
Today, I had pancakes for breakfast.
On Friday, I had pancakes for breakfast.
Whenever I visit my grandma, I have pancakes for breakfast.
If I have time to make them and have all the ingredients on hand, I have pancakes for breakfast.
Susan, I had pancakes for breakfast.
Yes, I had pancakes for breakfast.
You know, I had pancakes for breakfast.
(Note: it is sometimes okay to leave the comma out when the introductory element is only a word, like in my first example. But again, because it often is necessary to have a comma to be clear, I make it a habit to always use one, and I teach my students that, also.)
3) To set off interruptive elements in a sentence. This is anything that interrupts the main clause of the sentence – it could be a word, a phrase, or a clause. The important thing is that it is not necessary to the idea in the main clause; it is “parenthetical” material.
I had pancakes, the food of the gods, for breakfast.
I had pancakes, of course, for breakfast.
I, my dear, had pancakes for breakfast.
I had pancakes, which often give me heartburn, for breakfast.
I had pancakes that my mother made for breakfast. (NOTE: “That my mother made” is NOT set off by commas because it is not parenthetical; it is a necessary idea in the main clause. Sometimes you have to make a judgment call on that, but usually, if you try to put the phrase in parentheses, it becomes clear if it is parenthetical or not.)
I had pancakes for breakfast, the most important meal of the day. (NOTE: “The most important meal of the day” is not actually interrupting the main clause – it’s at the end. But it’s still an “interruptive element”; it’s just placed at the end instead of at the beginning or middle. So it still needs to be set off with commas, although the second comma becomes a period since it’s at the end of the sentence. See more examples to follow.)
I had pancakes for breakfast, Susan.
I had pancakes for breakfast, of course.
4) To join two independent clauses with a coordinating conjunction. This is the biggest bugaboo for commas, I think. I actually explained this in great detail in an earlier post (here), so I won’t elaborate too much. The important points are that each clause must be independent (a sentence that would stand on its own and make sense) and the conjunction you use must be a coordinating conjunction (use the acronym FANBOYS to remember the coordinating conjunctions: For, And, Nor, But, Or, Yet, So).
I had pancakes for breakfast, and I had waffles for lunch. (CORRECT)
I had pancakes for breakfast, and waffles for lunch. (INCORRECT – “waffles for lunch” is not a sentence that would stand on its own. Take out the comma.)
I had pancakes for breakfast, however I had waffles for lunch. (INCORRECT – “however” is not a coordinating conjunction. It is a conjunctive adverb. Remember FANBOYS.)
I had pancakes for breakfast, I had waffles for lunch. (INCORRECT – this is a comma splice. You can’t join two independent clauses with just a comma. Either change it to a semicolon, or add a coordinating conjunction.)
NOW, there are two caveats here. One, there are occasional, rare situations where a comma would not normally be grammatically correct, but where a sentence is unclear without it.
What the crew does, does affect our voyage.
If it looks like a bizarre mess without a comma, add one for clarity; however, your better choice is to reword the sentence entirely. (Our voyage is affected by what the crew does.)
Two, if you are a good reader, and especially if you read stuff by older authors or by more “poetical” authors, you will see these rules violated all the time. I know I always have to get a grip on myself when I read C.S. Lewis because he uses older punctuation rules, and it unnerves me for a moment. Punctuation rules are conventions, and they change over time.
So, there you are. Go, and punctuate likewise. J