A Writer's Guide to Punctuation: Commas

Used in many contexts and languages, the comma can be one of the most confusing pieces of punctuation for many writers and readers. The downstairs neighbor to the apostrophe, the comma comes in a familiar shape, but isn't always a familiar friend when it comes to those reading and writing in the English language. However, knowing when and where to place a comma can be direly important. In 2017, a Maine company lost $6.84 million in a suit brought by its because of a missing comma in a contract changed the meaning of the terms.

Even 43 out of 50 U.S. states mandate serial commas in contracts and legislation to ensure there is no ambiguity in language. While commas typically aren’t so costly for most of their users, mastering their usage is essential for anyone who wants to ensure they have clear meaning. For many, the tricky part is finding the balance between using too many commas and using too few. There are also a few subtle differences in how commas are used depending on what type of English one writes and speaks in. Over the years, British English and American English have developed a few contradictory comma rules as well.

Historical Background

The concept of the comma as well as the shape we all associate with the comma today haven’t always been a part of our accepted grammar. It wasn’t until around 200 BCE that the concept of punctuation was even introduced to Western grammar via Aristophanes of Byzantium, a Greek scholar and grammarian who most famously served as a librarian at the famed Library of Alexandria. The first punctuation marks he introduced were a series of three dots one located at the bottom of a line of text, one in a center, and one at the top that indicated how much breath a speaker or reader needed to take between words. This served more as a rhetorical device for talking aloud rather than meant to help keep meaning consistent.

It was the dot at the bottom that he dubbed a komma indicating a short pause between a thought or idea. The Greek word komma meant both “a clause in a sentence” but also was a term used for stamps and coins. The term literally translated from ancient Greek to mean “piece which is cut off,” from the Greek word koptein meaning “to strike, smite, cut off, disable, or tire out.”

The Romans and Latin changed the “k” to a “c.” Despite Aristophanes efforts to get the ancient Greek world thinking about where they paused in their sentences and how to indicate such pauses for future readers, it wouldn’t be until centuries later that punctuation caught on. One of the reasons why punctuation became popular was early Christianity and its reliance on making sure believers in different parts of the world had the access to the same documents and interpreted the same meanings from those documents.

This document shows a slash being used as a comma

The location of punctuation could easily change a meaning or interpretation of the text. One of the early punctuation marks they adopted was the virgula suspensiva which we might recognize as the diagonal slash or / mark. Sometimes this mark is still used in lyrics and poetry to indicate when and where a new line begins. The use of the slash may have originated from the fact that slashes or a double slash were often used in music to indicate pauses. Many early punctuation marks were borrowed from musical notations.

From about 1200 until about 1600, this slash mark served the larger purpose of the comma such as separating words, phrases, and clauses to help sentences be better understood. However, commas also began to evolve to perform functions such as setting up questions and putting emphasis on specific ideas or clauses. It was an Italian humanist, scholar, educator, and publisher who is credited with the creation of the comma shape we now identify today. While repetitive punctuation marks such as dots, slashes and lines made since when documents were handwritten, the advent of the printing press meant that it was easier for these marks to become confused.

To avoid confusion and improper printing, publishers and printing press operators began devising and popularizing new marks and symbols that were unique and easily distinguishable.Born Aldo Manuzio in Bassiano outside of Rome, the printer who would adopt the scholarly name Aldus Pius Manutius was born sometime in the mid-1400s and founded the famed Aldine Press, which was devoted to publishing and disseminating rare texts during the advent of the Italian Renaissance. He worked to preserve Greek manuscripts and ancient tests such as those by Aristotle and Aristophanes, which was a difficult task because there weren’t yet typefaces for these ancient languages.

Manutius also introduced the type of text that became the precursor to what we now know as italic type or text. Another one of the innovations of Manutius and his Aldine press was the mark we know today as the comma. He was one of the first to take the slash proposed as a comma and then drop it to the baseline of the text as Aristophanes had suggested. This put a tiny slash mark at the bottom between the letters. As text and typography developed, these little slashes became more stylized and evolved into the shapes we recognize now today as commas, apostrophes, and quotation marks.

The Oxford Comma Debate

One of the reasons the comma remains a contentious subject among scholars and grammarians even today has to do with a debate over one particular usage of the comma. Actually known as the serial comma but often referred to as the Oxford comma or Harvard comma, writers, editors, and scholars have debated over whether or not modern language still has use for this rule. British English doesn’t always make use of the serial comma, but in America its use is mandated by many style guides.

Additionally, some regional dialects of American English lend themselves to the usage of this comma whereas others don't. Commas are used to separate things in a list, but the Oxford or serial comma is used when that list contains a conjunction. For example, a sequence using an Oxford comma reads as “England, France, Italy, and Spain.” However, those who don’t believe in the use of the Oxford comma believe it is fine to write the phrase “England, France, Italy and Spain.” The issue comes in when the serial comma is needed for clarification. For example the phrase “He thanked his parents, God and David O. Selznick” implies that the person’s parents are God and David O. Selznick. However, the phrase with the Oxford comma - “He thanked his parents, God, and David O. Selznick” - shows that these are in fact separate people.

Those in favor of the Oxford comma argue that it is consistent with grammar historically, matches the way people speak more accurately, can resolve ambiguity issues, is consistent with how lists are made with other punctuation marks such as semicolons, prevents misreading of phrases, and that the lack of the serial comma may imply a connection that isn’t there. Opponents of the comma argue that it is actually inconsistent with conventional use, may introduce ambiguity, and adds unnecessary bulk to the text.

Those who write professionally often had different viewpoints on the use of the serial comma as well. Journalistic writers are less likely to embrace the Oxford comma because of the premium of space in their writing while academic and formal writers are more likely to use it. Despite this, many important style guides, including the U.S. Government Printing Office, advocate the use of the comma to prevent ambiguity. While most in Britain oppose it, the Oxford University Press encourages its usage - hence the nickname Oxford comma. Australia, Canada, and South Africa are more on the fence about serial commas, often suggesting that writers forgo them unless necessarily for clarity purposes.

The absence of a serial comma became the focal point of a dispute between a dairy company and its delivery drivers, ultimately costing the company millions and leading into a change in Maine state law.

It is the Oxford comma that created the more than $6 million loss to the Maine dairy mentioned earlier. The lack of the comma in a state statute reading "canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution" of certain goods was at the center of the legal debate, particularly the lack of a comma between packing for shipment and distribution. The case made it all the way to the U.S. Court of Appeals and ended up forcing the state of Maine to change the law for clarity.


Many guides say as a general rule of thumb to put a comma anywhere in a sentence where a speaker would naturally pause or take a breath, but this guideline isn’t always one that can be exactly followed. Speakers of different dialects often but emphasis on different parts of their speech as well as pause in different places. Likewise, not every long sentence needs a comma for it to make sense and the addition of commas may even confuse meaning whereas some shorter sentences may need commas for clarity.Additionally, one of the things that has added to all the comma confusion is the fact that we as a society use less of them than we used to.

Back when punctuation was first evolving in the Renaissance and Age of Enlightenment, it wasn’t uncommon for writers to pepper in punctuation marks wherever they pleased. Just like the ancients refused to use punctuation or even spaces between words, those in the 1600s and 1700s took the opposite hand, experimenting and liberally using punctuation to excess.

It has only been as more people become literate that a need for set standards of grammar and syntax have really come about as writers and readers have become more concerned with ensuring their works can be correctly and accurately interpreted by others. Here are some of the general rules that have involved using commas:


Sometimes, we use words or phrases to set up a sentence, to introduce the thought or idea that we are presenting. Often times, this can involve the use of adverbs or a singular word while other times it can use longer phrases and fragments. For example:

Yes, we have no bananas.

Moreover, my client was not present the night of the shooting.

Frankly speaking, you shouldn’t have asked in the first place.

Despite the fact that she had no experiences with obstacle courses, she volunteered to go first.

The parts of the sentence offset by the commas aren’t essential to the main phrase, but often can add more information or serve as a transition, underlining a thought, or provide emphasis. As general rules of thumb, most grammarians suggest using a comma to offset adverbs (mainly words ending in -ly) and those that they modify as well as any fragment that is more than four words but isn’t necessarily essential to the main thought.

Similarly, this rule applies to sentences that include a direct address. This is when a sentence directly calls out who or what it is speaking to. For example:

Mom, where are my glasses? Sweetheart, I don't know.

Separating Independent Clauses

Commas are also used to connect separate clauses or sentences that have a conjunction between them, but many writers often place commas in sentences without coordinating conjunctions. Words like and, but, and or are among the coordinating conjunctions where a comma is needed to link to phrases. Without a conjunction, there is usually no need for a comma. For example the appropriate use of a comma is with the sentence:

He walked into the room, and he sat down in the chair.

However, it would not be correct to write:

He walked into the room, he sat down in the chair.

This sentence could be written correctly either with periods or semicolons:

He walked into the room; he sat down in the chair.

He walked into the room. He sat down in the chair.

Likewise, it would be incorrect to write:

He walked into the room, and sat down in the chair.

The reason for this is there aren’t two nouns so it is implied that “he” applies to both verbs. The correct version is:

He walked into the room and sat down in the chair

Likewise, commas are not needed for comparison phrases that use words like "than," "then," or "that." For example, no commas are needed in sentences:

Her dress is more orange than I remember it being.

We are going to the movies and then to a restaurant.

We are going to a restaurant that serves French food.

Separating Out Non-Essentials

Similarly, commas can be used to separate out clauses, phrases, or fragments that aren’t essential to understanding the sentence. This can include dependent clauses that make no sense on their own or appositives with nonessential information. Dependent clauses are very similar to introductory clauses in that they aren’t always essential to the sentence but can give more meaning or emphasis.

Likewise, appositives are not essential phrases but can often provide clarity or more meaning in a sentence. Any time information is essential it is best to forgo the comma. Other times commas are used in this way are for interrupters, those little phrases that sometimes pop up in a sentence to indicate tone, emotion, emphasis or more information such as an aside. Often times, these are phrases that could be set into parenthesis, but many writers feel the use of parentheses can bog down a sentence and prefer commas for a smoother flow.

Examples of independent clauses set off by commas include:

In the event he dies suddenly, Rob has asked me to clear his browser history.

Build sometime during the 1700s, the house is the oldest structure in our town.

Whereas an appositive, interrupters or asides include:

Megan, who graduated high school with a 4.0, will be studying abroad in Greece.

My father, who worked at an auto dealership for 40 years, is enjoying his retirement.

John, who doesn't look as bad in real life as he does in this picture, is my best friend.

However, in phrases like:

The Packers whose uniforms are green stood out among the white snow.

The actor Alistair Sims played one of the best versions of Ebeneezer Scrooge.

The comma isn't needed because the appositive provides essential important.

Separating Out Quotations

Quotations are one of the ways we demonstrate direct attribution to a phrase, thought, idea, or sentence. Very important in journalism to separate what someone really said versus a summation or paraphrase of their ideas, writers of fiction must also master the quotation comma for the clarity of their readers. Commas and quotation marks often go hand-in-hand as a result. However, the position of the comma may depend on where in the quote the attribution has gone.

For example, at the beginning of a sentence, it could be written:

And then John said, "I am not sure about this. We could get in trouble."

But more proper might be the use of a colon:

And then John said: "I'm not sure about this. We could get in trouble."

If the attribution comes in the middle of the quote or end of the quote, the quote ends with a comma and then a period after the attribution to indicate that John is not only saying what comes before but also what comes after.

"I'm not sure about this," John said. "We could get in trouble."

"I'm not sure about this. We could get in trouble," John said.

This is the case unless the attribution interrupts a single sentence or thought. Then another comma goes after attribution to indicate the person is still speaking.:

"I'm not sure," Jane smirked, "he has all the information."

Connecting Modifiers

Just like conjunctions connect two phrases together, commas can also be used to connect together similar words. A pair or more of adjectives, verbs, and adverbs that modify another word are offset by commas to avoid confusion or causing readers to put two words together that don’t belong together. Examples include two or more adjectives that modify a singular noun such as:

She found an old, rusted car.

He smiled with a big, lazy grin.

A series of verbs describing action:

He ran, tripped, and fell over.

She hopped, skipped, and jumped.

A series of adverbs:

He knelt slowly, surely, and without thought.

This not only a rule for modifying words but also phrases known as free modifiers. There are several types of free modifiers including initial modifiers, resumptive modifiers, and summative modifiers. The one thing all these modifiers have in common is that they often refer to other parts of the sentence or thought, adding to the ideas within them. A free modifier is simply a phrase or clause that modifies a main idea or even another free modifier, usually following a verb by commenting on the subject or noun of the sentence.

Like the term sounds, initial modifiers are modifiers that come at the beginning of a sentence. The include initial modifiers at the beginning of sentences such as:

Even though he was tired, he woke up when his alarm went off.

While we went shopping, she cleaned the house and took out the trash.

Resumptive modifiers are modifiers that often repeat a word or idea for emphasis such as:

It was there I ate my first piece of sushi, sushi that would change my life.

He grimaced at the woman, a woman who had caused him so much pain.

While summative modifiers are those that come at the end of the sentence, often summing up an idea or theme. Examples include:

The restaurant had excellent garlic bread, making us more likely to return there.

His senior year he joined the baseball team, forging lifelong friendships.

Contrasts, Shifts and References

Commas are often used to show a shift in tone, contrasting clauses, or to offset negative clauses within a sentence. The term negative clauses doesn't mean that the clause itself has to be negative in any way, but rather that these clauses often provide information that is the opposite, contradictory, or contrasting to the phrase or sentence before them. For example:

He brought her roses, not dahlias.

The children were polite, if messy.

The restaurant's offerings were good, though I don't think we'll eat there again.

Likewise, commas are also used to set off phrases or clauses that refer to another part of the sentence or idea. This can include questions such as:

They don't shoot horses, do they?

He will bring back my book, won't he?

Indicating a Series

This is the area of commas where the dreaded Oxford comma debate comes into play, but regardless of whether or not you support the Oxford comma, there are still commas needed in series of words. For example:

He went to the grocery store and bought apples, oranges, and peaches.

He went to the grocery store and bought apples, oranges and peaches.


Another one of the more confusing questions about commas comes with titles. A title doesn't have to be someone's professional designation. It can even be a phrase that describes an objects roles. Professional titles or descriptive phrases of a person that can serve to give more information about their role generally involve the usage of commas. Examples include:

Dr. Sarah Schneider, director of the non-profit, says donations are declining.

A Newark housewife, Deborah Simmons, says she often visits the park.

He also spoke with Luis Valdez, his lawyer.

However, if the occupation or title isn't rare or unique, it is acceptable to forgo the comma for clarity. For example:

Newark housewife Deborah Simmons says she often visits the park.

He also spoke with lawyer Luis Valdez.

The tricky part is that slipping up with title commas may led readers to interpret things in correctly. For example saying:

Mark and his wife Julie attended the party.

may indicate that Mark has multiple wives of which Julie is one. Despite this, many writers believe that the technically grammatically correct phrase:

Mark and his wife, Julie, attended the party.

bogs down the sentence. Therefore, the commas are not serving the purpose of providing clarity and should be eliminated. However, it should also be taken into consideration what readers might interpret. For example, the phrase

Sampson and his brother Paul came to the party as well.

indicates that Paul is Sampson's only brother whereas writing:

Sampson and his brother, Paul, came to the party as well.

indicates Paul is one of two or more brothers Sampson has.

Things change a bit with there is a modifying word involved. For example, it is correct to say:

Mark came to the party with his wife Julie.

But you would add a comma phrases:

Mark came to the party with his second wife, Julie.

Julie's first husband, Paul, was not pleased to see them there.

Other Uses

There are several other general uses for commas that follow the general rule for helping apply clarity to sentences. These include using commas with geographical names, addresses dates, and numbers over 999. Examples of geographical names and addresses include:

She lives in Minneapolis, Minnesota.

The Seattle, Washington-based business.

Paris, France, is where she was born.

Baltimore, Maryland, was the first location on his list.

Notice that if there is a phrase after a state or country a second comma is also included where as if the state is modifying such as "Washington-based" there is not. Addresses also use commas:

123 Main Street, Anytown, USA

1066 Pennsylvania Avenue, Washington, D.C.

Date are one of those tricky situations where American and British English different a bit, not necessarily on comma rules but on how they are stated. An American date puts the month first followed by the day followed by the year whereas British dates put the date before the month and then the year. It is only in the American version that commas are needed because they offset two numbers. For example:

July 4, 1776

4 July 1776

Regardless of which type of English one speaks or writers in, days of the week will always be set of by a comma when writing a date.

Tuesday, January 2

Friday, October 13

Likewise, commas also set off numerals over 999 to make numbers more clear:



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