People often make the same few errors in their writing. Stanford writing researchers — Andrea and Karen Lunsford — have identified the “Top 20” errors. (You can see them here.)
Of these “Top 20 Errors,” seven of them are because of a problem with a comma. Writers omit the comma, put it in the wrong place, use a comma when something else is needed, or use a comma when it’s not needed.
This study shows that commas cause a lot of problems. I see this in my editing work as well. When I edit and proofread someone’s book, article, job application letter, blog, or social media post, problems with commas are the most frequent. I feel like I am always pointing out a missing or incorrect comma.
This study also shows that you can dramatically improve your writing by using commas correctly. If you do nothing but fix all of the comma errors, you will eliminate 7 of the Top 20 Errors in your writing.
Major and Minor Uses
There are around 20 occasions when you need to use a comma. Many of these are considered “minor uses” — that is, omitting a comma for this occasion doesn’t cause a major problem with the writing. Here are some examples:
Dates: January 1, 2021
Location: Chicago, IL
Large Numbers: 12,000
Addressing a Person: “Grandma, would you like some coffee?”
Salutation in a Non-Professional Email or Personal Letter: “Dear Susie,”
Before or After a Quotation: “We are all Americans,” said the president.
Between Two Adjectives: “The quiet, studious musicians were brilliant.”
These are examples where a comma is the correct punctuation to use. But, if you omit the comma or accidentally use a different punctuation, it doesn’t mess up the whole sentence. It can be easily fixed.
Major-Important Uses of the Comma
There are also more “important” or “major” uses of the comma. In these occasions, an error with a comma causes more problems. The sentence is difficult to understand, and the sentence ends up having a major error where the whole sentence is problematic.
In a writing class, these errors would count as major “sentence-level” errors instead of as a simple punctuation error. Understanding how to use these “important” commas will dramatically help improve your writing.
1. Separate Items in a List
One of the most frequent uses for a comma is to separate items in a list. Use a comma in between each item when there are three or more items. Here is an example:
Remember to maintain “parallelism” when making a list. That means that each item in the list should have the same grammatical unit - such as all nouns, all verbs (in the same tense - such as past, present, or future), all prepositional phrases, adjectives with nouns, and so on. The example above shows all nouns (types of punctuation).
Should I use a comma before the “and”? Yes! It is acceptable with some writing styles to omit the final comma (the one after “period”). However, a more traditional writing style requires that you use it.
I like to use the comma at the end because it makes the three or parts more clear. Otherwise, without the comma, you may accidentally group the last two items together.
Here is an example. How many sandwich types are there?
In the first option - without final the comma - it kind of looks like there are three sandwich types: PB&J, Turkey, and Ham & Roast Beef. But in the second option, it looks like there are four sandwich types: PB&J, Turkey, Ham, and Roast Beef. The final comma makes a difference on whether Ham and Roast Beef are two separate sandwiches or only one sandwich with two types of meat.
A menu item like that could confuse customers in a restaurant. The restaurant owner may end up giving sandwiches with double meat if the menu doesn’t use the final comma. Of course, the server could explain that it’s really meant to be four types of sandwiches, not three, tut it would be much easier to use a comma and avoid the confusion.
2. Join Two Complete Sentences with a Coordinate Conjunction (FANBOYS)
Another important use of the comma is to join two sentences with a coordinate conjunction, such as for, and, nor, but, or, yet, so. The comma goes after the first sentence, and it is followed by one of these conjunctions - they are also called FANBOYS.
Remember that the two sentences that are joined need to be complete sentences; one of them can’t be a sentence fragment or a dependent clause. In this example, both sentences have a noun and a verb (“educational books have” and “novels don’t include”). Without a subject and a verb, the sentence is incomplete, and the writing has another major error.
Check out my previous newsletters about writing simple sentences and joining sentences for more information.
3. After an Introductory Element
An “introductory element” is a transition or a prepositional phrase at the beginning of the sentence. Traditionally, a comma goes after this word or phrase. Here are some examples:
These transitions help make the writing more cohesive by adding a “flow” between sentences. At other times, a transition like “however” could reverse the flow of the writing.
It’s acceptable to omit the comma with a date or with some short preposional phrases, but I like to use the comma anyway because it helps to show where the introductory phrase ends and where the main part of the sentence begins.
Otherwise, don’t make introductory elements too long; they should not be more than about 5 to 7 words long. If it’s longer than that, consider writing a full sentence or combining two sentences with a subordinate clause.
4. After a Subordinate Clause
A “subordinate clause” is a sentence that begins with a “subordinate conjunction,” such as although, because, before, after, since, if, when, and many more. (See a list of subordinate conjunctions and sentence examples in my previous newsletters.)
The comma goes after the sentence that starts with the subordinate conjunction. Here are some examples:
The part of the sentence with the subordinate conjunction (the sentence on the left) is called the “subordinate clause” or the “dependent clause.” This part is less important than the main part of the sentence on the right. That means that the major or main part of the sentence needs to go on the right.
In the first example sentence above, “I didn’t get to mow the grass” is probably the main message, so this sentence is correctly placed on the right. But, in the last sentence, “taking the antibiotics” is probably the main idea of the sentence. In this case, the order of the two parts is probably not correct because the part about taking antibiotics needs to go last. As a result, the sentence may need to be reversed and read something like “We didn’t feel better until we took the antibiotics.” (This type of sentence does not need a comma.)
5. Designate Non-Essential Information
Last week’s newsletter about writing complex sentences also showed that the “dependent/subordinate clause” can be placed in the middle of the sentence. When it does that, it is considered “non-essential information,” and a comma is used at the start and end of the clause. Here is an example:
The “non-essential information” typically goes after a noun, and it provides additional information about the noun. In these examples, the non-essential information adds additional details about grandma and about the church.
What if the information is “essential”? If the information about the noun is important, don’t a use comma. Here is a very common example:
In this example, “who are pregnant” is not extra information about women. Instead, that information is part of the identity of the subject. That is, the subject is “women who are pregnant,” not only “women.” This sentence is specifically about “women who are pregnant” and not only about “women.” So, in this case, the phrase “who are pregnant” is essential information, and the commas are not needed.
Review
The comma is one of the most useful and versatile punctuations. Knowing how to use commas can help you improve your writing dramatically — using commas correctly can help you avoid 7 of the “Top 20 Errors” in writing.
Here is a summary of the minor and major uses of the comma described in this newsletter.
Now, go through a document, email, or social media post you have written, and see if you have made any comma errors. Then, fix them. After you fix them, email me the following information (or post a comment below):
The original sentences with the comma error.
A short explanation of what type of comma error you have found.
A revised, fixed version of the sentence.
If you paid attention, you may have noticed that the sentences below the table, which provides a review of this newsletter, use all five major uses of the comma! Can you find them?
Thank you for reading my newsletter. I taught writing for over 10 years, and I offer editing and proofreading services. Have you always wanted to write your book, website, or social media profile? Do you have ideas and rough drafts, but you don’t know how to put them together? Contact me, and let’s make a plan. And subscribe to the newsletter for more writing strategies.