This is the first blog in my punctuation blog series, so I am starting with a more basic rule. Every punctuation blog will cover just one topic in depth and have an exercise at the end to practice the concept.
Coordinating Conjunction: Say What?
First, let’s get the technical jargon out of the way. A coordinating conjunction is a “word that joins together words or word groups of equal grammatical weight.” (Merriam-Webster)
So technical jargon and definition aside, let’s call them FANBOYS because the coordinating conjunctions are for, and, nor, but, or, yet, so.
When you are listing out items in a series, the last item is proceeded by an “and” or an “or.”
Each item in the list is separated by a comma, but the Oxford (or serial) comma, the last comma before the conjunction, may be omitted, depending on the style guide you are following and personal preference. Some, like me, never omit the Oxford comma. (Warning: Don’t ask about the Oxford comma to a group of editors or serious grammar lovers, it will spark a vicious debate.)
Some style guides suggest you wouldn’t need the comma before the “and” in either of these sentences because the “and” acts as the separator between the last two elements. However, I follow Chicago Manual of Style which encourages always using the Oxford (serial) comma for consistency. Plus, I personally think it looks cleaner.
But both are technically correct without the comma. (It hurt me a bit to say that.)
If you prefer not to have the Oxford comma, just note that all style guides will agree sometimes it is needed.
Without the Oxford comma, it reads like Jessica and God are the person’s parents; however, the author really meant the book was dedicated to their parents, to Jessica, and to God.
In between Clauses
FANBOYS are used to join phrases and clauses, not just items in a list.
An independent clause is a complete thought with a subject and a verb—basically a sentence.
A phrase does not contain both a subject and a verb, so it is not a complete thought.
RULE #1: When a FANBOYS is joining phrases, no comma is needed—but you can opt to have a comma for stylistic reasons.
RULE #2: When a FANBOYS is joining independent clauses, you will need the comma. You can’t have just a comma between two sentences nor can you have just a FANBOYS. You need both.
Take a look at these two sentences and note the use of a comma before the FANBOYS in one sentence and the lack of comma before the FANBOYS in the other.
Note: I have underlined the subject and double underlined the verb.
Since this blog is discussing the rules, I will call these errors. But sometimes authors intentionally break the rules for stylistic reasons; however, when it isn’t for a good reason, then it is an error.
When you break rule #2, you could end up with a run on or a comma splice.
Comma splice: Independent clauses joined with just a comma.
Run on: Independent clauses joined with just a FANBOYS.
Now you know what a run on really is; it is not a long sentence. It is a sentence that should have a pause indicated by a comma, but it doesn’t, causing one to run on and on through the sentence.
A run on could be a long sentence: I love punctuation marks for they are fun to play with but sometimes the rules trip me up and I get frustrated with them.
But what makes that sentence a run on is not the length. It is a run on because you have FANBOYS in between sentences without a comma. In fact, there are three FANBOYS joining independent clauses.
A little about stylistic choice
After I finish my punctuation series, I will end with a fun blog post on breaking the rules for stylistic reasons. But for now, here is one stylistic choice.
While a comma usually does not proceed a FANBOYS when joining phrases, one might choose to add one for dramatic emphasis.
A Note About “So”
While “so” is a coordinating conjunction, it also has other functions, and as a conjunction, it has two definitions.
So as a conjunction could mean “and for that reason” (therefore).
So as a conjunction could mean “with the aim that or in order that.”
When it is used as the first definition (therefore), a comma is used. When it is used as the second definition (that), a comma is not used.
Assessing Your Understanding
Take this quiz to check your understanding of the rules.