Are there too many commas in your writing? Not enough? Where do you need them and when? “Comma confusion” is one of the most common grammatical problems I find in manuscripts. Here are some quick tips to help you determine whether a comma is really necessary — and if so, why and where.

One way to help identify “right” and “wrong” punctuation is through substitutions. If you can substitute the item for which a bit of punctuation is “standing in for,” you have the correct punctuation. If you can’t… you don’t.

Run-on Sentences

Let’s start with commas and “run-on sentences.” A “run-on” sentence is one in which several complete phrases are strung together with commas. Each phrase is in itself a complete sentence. But when they are strung together, what they form is not a complete sentence.

Here’s an example, here’s another example, here’s a third example.This is not, in fact, a sentence. How can you tell? Try substituting a period for the commas.

Here’s an example. Here’s another example. Here’s a third example.Notice that each sentence stands alone just perfectly. If you can substitute a period for a comma, then something is wrong with the comma. Here’s an example in the reverse, using the sentence I just wrote: “If you can substitute a period for a comma, thensomething is wrong with the comma.” Try the replacement here:

If you can substitute a period for a comma. Then something is wrong with the comma.See? Neither of those two sentences stands alone (particularly the first). That’s a good indication that you do need a comma!

Another substitution you could make is using the word “and”:

Here’s an example and here’s another example and here’s a third example.This is a grammatically correct sentence. It isn’t a good one, but it’s correct. It’s also getting you closer to the sentence you were trying to write. The next step is to swap those “ands” for commas… with one huge exception:

Here’s an example, here’s another example,and

here’s a third example.This is the famous “serial comma,” which is what you were aiming for in the first event. Note that you only actually had to make one change to your sentence to make it correct: insert that little “and” in front of the very last clause. That’s all that was needed to change a bad sentence to a good one.

Incomplete fragments

Another common comma misusage is to have the impression that “I just know a comma is needed here somewhere, but I’m not sure where, so, I’ll, just put in a couple and, hope for the best.”

Let’s start with the “period/comma” substitution test and see what happens:

I just know that a comma is needed here somewhere. But I’m not sure where. So. I’ll. Just put in a couple and. Hope for the best.The first two clauses do, in fact, stand alone, so you can leave those commas alone. Technically, you could even leave “So” alone — it’s called an “interjection” (like “Aha!” and “Hey!”), and thus could stand alone if you absolutely wanted it to. In other words, you could leave a comma after it, or you could remove it. (The key there is to ask whether you actually want the reader to “pause” after reading “so”; if you do, leave it in; if you don’t, leave it out.)

After that, well, it’s pretty obvious that you don’t have complete sentences. So start taking out periods and see what happens:

So I’ll just put in a couple and hope for the best.Whoops, no more commas! In fact, none were needed.

Now a quick digression: Some people object highly to starting a sentence with “but” or “and.” I am not one of them. I don’t think it should be done often, but it can be done — as it does. create a “complete thought.” An alternative is to use “however,” but this can create a more complicated sentence and isn’t always what you want. “However” will nearly always need to be followed by a comma; “but” does not:

“But I don’t know what to do.”

“However, I will soon find out!”

Dependent clauses

One of most common uses of a comma is to set off a “dependent clause.” A dependent clause is a part of a sentence that can’t live on its own. It needs life-support. It generally does not have its own subject, or quite often even its own verb, like that clause I just inserted. It doesn’t make sense without what went before.

Without commas, a dependent clause contributes to a run-on sentence that is very hard to understand. The commas tell you “hey, listen up, new thought or idea coming here!” The primary problem with dependent clauses is forgetting to “close” the comma. If a dependent clause occurs within a longer sentence, it must open and close with a comma.

You can quite easily identify a dependent clause with the “period” substitution — you’ll instantly see that you don’t have complete sentences. But you can’t expand on this substitution by inserting an “and” — so now what? Try the next item on your substitution menu: The parenthesis. A dependent clause can be set off with a parenthesis and still be correct:

It generally does not have its own subject (or quite often even its own verb), like the clause I just inserted.Note that I did put a comma after the parenthesis, because in fact both the second and third clauses in that sentence were dependent. The only “standalone” clause was the first; it is the one that had a subject and a verb.

Once you identify a clause that can be set off with parentheses (which clearly must be opened and closed), it’s much easier to determine where you need to put that second comma. You could also choose to leave the parentheses, or you could use dashes (which also have to be opened and closed):

It generally does not have its own subject — or quite often even its own verb — like the clause I just inserted.In this case it becomes understood that the third clause is dependent, as you never put a comma or any other punctuation directly before or after a dash.

The Apposite Phrase

One common area of “comma confusion” is the apposite phrase. An apposite phrase is a type of dependent clause that further defines the subject (or object) of a sentence. It is an element of description that may add to the information that you are providing, but that could be removed without badly damaging the sentence. Sometimes it is hard to distinguish between an apposite phrase and an ordinary “clarification” or bit of description.

One of the most common places in which there is confusion is over things like introductions, like the following:

“John, this is my wife, Mary.”

In this case, “Mary” is an apposite phrase and must be set off with a comma.“John, this is Mary, my wife.”

In this case “my wife”technically

is an apposite phrase, as you couldn’t use this without a comma — but it’s clumsy. Presumably the speaker is explaining to John that Mary is his wife, but you could still use the sentence without the second phrase.“John, this is my sister, Joan.”

This is an apposite phrase because it suggests that the speaker only hasone

sister, whose name is Joan. The name provides more information, but it is still directly synonymous with “my sister.”but

….“John, this is my sister June.”

This is not an apposite phrase because it is suggesting that the speaker has more than one sister (perhaps Joan and June), and the speaker is therefore clarifying not only that this is his sister, but which sister it is. If you put a comma here, you would be implying that the speaker only has one sister, named June. Without the comma, you are indicating that the speaker may have several sisters and you must clarify which it is.

An apposite phrase is one that can often be dropped without damaging the structure of the sentence or badly obscuring the meaning. Thus, if you write: “British novelist Jane Maladroit…” you do not need a comma between “novelist” and “Jane,” because you can’t actually drop the words “Jane Maladroit” without badly obscuring the meaning of the sentence. There are many British novelists; there is only one Jane Maladroit. So, as with the “my sister June” example, you need to keep the name in the sentence to make the sentence clear.

However, you could write: “Jane Maladroit, British novelist..” as an apposite phrase (with the commas), because in this case, you are saying Jane Maladroit = a British novelist. The words “British novelist” are an added bit of definition to the subject “Jane Maladroit “, and while they’re helpful, they could be removed without damaging the sentence too badly. You could write, “Jane Maladroit won the prize,” and the reader would understand the sentence and come away with the information needed. But you couldn’t say “British novelist won the prize” and provide nearly as much information.

So here’s a quick and easy way to test whether something is an apposite phrase or not. Can you put in an “equal sign”?

“My wife = Mary” – you probably only have one wife (fewer if you are female).

“My sister = June” – this works only if you have only one sister

“Our sister site = LoadsofSisters.com” – this works if you have one sister site.

“Jane Maladroit = British author” – this works if Jane is a British author.

“John Smith’s new book = Understanding the Comma” – this is a bit “iffy” but works if John Smith has only brought out one new book recently.

Here are some phrases where you can’t put in an equal sign:

“My sister > June”

If you have more than one sister, then you arespecifying

which sister you are referring to; therefore, sister – June.“British author > Jane Maladroit”

There are many British authors, so you could not remove the information “Jane Maladroit” and keep the same meaning.“John Smith’s book > Understanding the Comma”

If John Smith has written many books, this clarifies which one you are referring to and is therefore essential.Note that an apposite phrase is nonessential information, even if it is useful. Commas are a common way to set off nonessential information — they tell the reader, “everything between these two bits of punctuation clarifies what went before.” Keep in mind that this kind of phrase must be opened and closed with a comma — “Jane Maladroit, British novelist, won the prize,” not “Jane Maladroit, British novelist won the prize.” You would say “My sister June went to the fair, while my sister Joan went to church,” but if you have only one sister, you would say “My sister, Joan, went to church” (because you could remove what was between the commas).

Now, one more bit of confusion: You can sometimes avoid the whole comma issue by putting the apposite phrase before the subject:

• British novelist Jane Maladroit won the prize.
• American writer Moira Allen wrote a lengthy treatise on apposite phrases and had the nerve to call it “short.”
• British writer Anne Nonymus often wished American writer Moira Allen would shut up already.

In these cases, the phrase really stands as an adjective (which is, at rock bottom, what an apposite phrase is, and that was one). It can’t always be done, but one way to test whether something is an apposite phrase and needs to be set off by commas is by testing to see if you can turn it around this way and retain the same meaning.

Apposite phrases can in fact be very long. Think of them as very long adjectives:

The writers we are attempting to reach, who often run their own (very successful) businesses, expect high quality material.Note that in this case an apposite phrase (who often run….etc.) interrupts a complete clause. You can’t cut the third part of the sentence and still have it make sense. You can cut the middle part and have it make sense. Thus, the middle is not only dependent, but it “defines” the object of the first part of the sentence (it defines “writers”).

And that brings me to the semicolon…

I know, I know: A semicolon is not a comma, even though it rather looks like one. However, when one is confused about where to put commas, one is often tempted to try to slap in a semicolon and hope it will solve the problem.

The best way to understand a semicolon is to realize that it really is a substitute for a period. A semicolon is the “legal” way to join two standalone sentences. If you do it with a comma, you have an incomplete sentence. If you do it with a semicolon, you have a complete sentence. Could you have done it with that last sentence above? Try it:

If you do it with a semicolon; you have a complete sentence.Why not? Try the period substitition:

If you do it with a semicolon. You have a complete sentence.In fact, you now have only one complete sentence (the second one). The first is incomplete — so, it requires a comma. You have, in fact, a dependent clause at the beginning of your sentence (it starts with “if”).

For a semicolon to be used, both clauses must stand alone:

John went to the movies; then, he had dinner at a fine restaurant.Note that you can substitute a period for the semicolon. If you tried to substitute a comma, you’d have a run-on sentence.

Another use of the semicolon is to separate lists that include lots of commas, hence:

We visited Detroit, Michigan; San Francisco, California; and Chicago, Illinois.Without the semicolons, each of those items has equal value and there is nothing to inform the reader that “Detroit” and “Michigan” are not, in fact, two different cities. Keep in mind that there are many potential readers outside the US who may not know the names of US cities and states (and, unfortunately, there are quite a few folks within the US with the same problem). Another example:

He ordered fish, liver, and chips; bought books, paper, and pencils; and visited his aunt, uncle, and sister.Which brings me to another disputed issue: Do you need a comma before the “and” in the serial comma? It all depends on when you were raised. If you were raised in my generation, the answer is “no.” However, later it seems that people became confused over the lack of this comma, and it seemed easier to just put it in than to try to explain it all the time, so it is becoming standard. I don’t care for it because it introduces a pause where you don’t necessarily want one, and it is correct to omit it — but copyeditors will often stick it in even if you don’t want it!

Commas and Other Punctuation

A final source of “comma confusion” is where to place commas in conjunction with other forms of punctuation, such as quotes, parentheses, etc. Again, substitutions can often help here.

A mistake I often see is to place a comma before a dependent parenthetical clause, like this:

John went to the restaurant, (which was open late) greeted the waiter, and ordered a hamburger.In this case, the parenthetical statement is a clause modifying the term “restaurant.” You could, if you wished, remove it and still have a complete sentence. Part of the confusion here arises from the fact that if you so desired, you could remove the parentheses and use commas in their place:

John went to the restaurant, which was open late, greeted the waiter, and ordered a hamburger.I suspect that what may confuse the writer at this point is the sense that you are almost putting a comma after a comma substitute. By using the trusty “substitute a period and see what happens” technique, however, you can easily see where the comma has to go:

John went to the restaurant. (Which was open late) greeted the waiter, and ordered a hamburger.The first half of the sentence makes sense, which means that a comma must not have been needed here. The second half of the sentence doesn’t make sense, which means something clearly is needed. The correct approach is to close off your entire “thought” before starting a new one, whether that thought has elements in parentheses, brackets, dashes, or commas:

John went to the restaurant (which was open late), greeted the waiter, and ordered a hamburger.But what about punctuation that belongs inside parentheses? It may look a bit silly to have “closing” punctuation both inside and outside parens, but it is necessary. The punctuation within parens should apply only to that specific phrase, while the punctuation outside the parens applies to your sentence as a whole:

I wanted to write a story about John (but it really got away from me!).Does it really matter? Does anyone care where your commas are? There are many who feel that such “nitpicking” over grammar is strictly for straitlaced purists. The bottom line, however, is that the task of writing is to communicate. We can never assume that our readers will, somehow, figure out what we mean; if we aren’t sure, how can we hope that they will be? Punctuation is simply a tool that enables one to make oneself understood on the printed (or electronic) page.

Moira Allen is the editor of Writing-World.com and the author of more than 300 published articles. Her books on writing include Starting Your Career as a Freelance Writer, The Writer’s Guide to Queries, Pitches and Proposals (Second Edition), and Writing to Win: The Colossal Guide to Writing Contests.