To Comma or Not to Comma? That is the Question

I am constantly encountering one grammatical error in unpublished manuscripts and even traditionally published books that I’d like to address here.

But before I answer that question, here are two definitions that will be useful in understanding this comma dilemma. The first definition is for “independent clause.” An independent clause is a string of related words containing a subject (a noun, pronoun, or proper name) and a verb (the action the subject is taking). This string of words can stand alone as a sentence. Example: My stomach grumbled. “Stomach” is the subject, “grumbled” is the verb.

The second definition is for “dependent clause.” A dependent clause is a string of related words containing a verb but CANNOT stand alone as a sentence. That last bunch of words following the “but” in the previous sentence is a dependent clause. Some sentences are simple independent clauses. Some sentences are two independent clauses connected by “and” or another conjunction (but, so, because, for). Some sentences pair an independent clause with a dependent clause. The two-independent clause sentence gets a comma before the conjunction for clarity. The independent clause + dependent clause sentence does not.

Let’s see some examples:

I made my lunch and stowed it in my backpack. (Independent clause plus dependent clause. In this case the “and” is connecting the two verbs carried out by the subject of the sentence  – “made” and “stowed.”)

Test: Does “stowed it in my backpack” stand alone as a sentence? No, it is a dependent clause. The verb in the phrase refers back to the subject in the previous clause. The rule: Do not use a comma to separate the verb from its subject.

My mother packed my lunch, and I forgot it on the counter.

Test: Forget the fact that you should have made your lunch yourself – your mother has better things to do, can the two strings of words on either side of the “and” stand alone? Yes. The rule: Two independent clauses connected by “and” require a comma.

Now that you know the rules, try punctuating these sentences (I am not giving you the answers because I think now you know):

I entered the biology lab and realized it was frog-dissecting day.

Frogs croaked from every corner of the room and my stomach churned.

I was too upset to eat lunch so my tuna sandwich moldered in my backpack.

(The above is meant as a bit of a trick. I didn’t use “and” as the conjunction, I used “so.” Same rules apply.)

The kids kept their distance because my backpack stank.

(Another curve ball – instead of “and” or “so,” the conjunction is “because.” Same rules apply.)

I walked in the door and gasped to see ants swarming my forgotten lunch.

I was still hungry so I went to the deli.

The above sentence could be an exception to the rule: Both independent clauses are pretty short. You could probably leave the comma out.

And finally, every story needs a happy ending:

I couldn’t decide between turkey or salami so I ordered a salad instead

One other exception to the rule (English grammar is full of ‘em), is even if the independent clauses are short, you may need the comma for clarity. Example:

I picked up the stinky bag and the flies followed.

Wait! Did I pick up the bag AND the flies? No, “the flies” is the subject of the second independent-but-short clause. So, to avoid misreading, use the comma.

Once you apply these rules to that tricky comma before the “and” question, you will know the answer: Independent clause + independent clause, yes. Independent clause + dependent clause, no.

If you have any grammar questions you want parsed out, let me know! Now go have lunch!