Copywriting Grammar Review: When to Use Commas

In 2018, a Maine-based dairy company paid out a $5 million settlement to 120 of its truck drivers.

The reason? The dairy company failed to use the Oxford Comma correctly in its drivers' contracts. 

This case points to the importance of correct comma use in legal writing. But lawyers and big companies aren't the only professionals who need to know when to use commas.

Commas are also essential to copywriting.

If you're blanking on commas and their purposes, here's a little grammar review: a comma is generally used to denote a pause between separate clauses. 

Commas can help make lengthy sentences easier to read.
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But exactly when should you use a comma when writing copy? We're laying out the comma rules copywriters need to know next, so you better keep reading.

When to Use Commas in Copywriting

We write with commas, as with all copywriting grammar conventions, to create clarity. Commas cause readers to take a pause. They make it easier to communicate the point we're trying to get across. 

In general, professional copywriters should use commas anywhere you might naturally take a breath if speaking the sentence aloud.

However, it's also a good rule of thumb to only use a comma when grammar conventions require one.

When do the rules of grammar mandate commas? We've outlined the top comma copywriting tips you didn't learn in ad school below.

​That way, you can avoid some of the most common grammar mistakes copywriters make.

​Distinguishing Between Independent Clauses

Clauses contain a subject (the noun) and a predicate (the verb). They can stand alone as a single sentence. Or clauses can connect together via conjunctions like but, and, or yet. 

Always use a comma when connecting two clauses together with a conjunction.

​For example, "it was my birthday and so I made a cake" would be incorrect. "It was my birthday, and so I made a cake" is the right way to write the sentence.

Sorting Out Elements in a Series

In the US, it's generally standard to offset items on a list with commas. 

​For example, "I'm going to pick up oranges, bananas, and milk at the store" is correct. "I'm going to pick up oranges, bananas and milk at the store" can also be correct in some circumstances. 

The difference between the two sentences is their use of the Oxford Comma. The Oxford Comma is a comma placed between the penultimate item in a list and the "and" separating it from the final item in the list. 

Which way is best — Oxford Comma or no Oxford Comma? We'll talk more about the Oxford Comma debate for copywriters below. 

Following an Introductory Prepositional Phrase

A prepositional phrase is an incomplete clause modifying the sentence's verb or noun. The prepositional phrase consists of the preposition itself (of, when, during, etc.), the object of the preposition (a noun), and any object modifiers. 

A comma should almost always offset prepositional phrases when they come at the beginning of the sentence. We say almost always because a comma is only needed if the phrase is four words or longer. 

For example, "When we go out, we always take the bus" would be correct.

But "When going out we always take the bus" would also be correct. 
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Keep in mind that you don't have to offset with commas prepositional phrases in the middle or at the end of a sentence. For example, "We always take the bus when we go out" would be correct.

Setting Off Modifying Phrases

A modifying phrase is an incomplete clause giving information about a word in the same sentence. Modifying phrases can be essential or non-essential. 

Essential modifying phrases give information that, if removed, would change the meaning of the sentence. Non-essential modifying phrases can be removed without changing a sentence's meaning. 

Always use commas to distinguish a non-essential modifying phrase in a sentence.

For example, "I ran, not very quickly, to catch the bus." Another example would be, "The bus, which runs only on Saturday and Sunday, was late today."

You should also always use commas to offset non-essential participial phrases. Participial phrases almost always modify the sentence's noun. Although these phrases can sometimes modify other nouns in a sentence.
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For example, "Running late, I tried to catch the bus before it left" is correct. "I tried to catch the bus before it left, running late as always" is also correct.

Splitting Up Adjectives

Adjectives are descriptive words used to modify nouns. Sometimes, you may need more than one adjective to describe your subject. In this case, the adjectives could be cumulative or coordinate.

You can easily recognize cumulative adjectives because adding a conjunction between them doesn't sound natural. Cumulative adjectives don't require extra commas. 

For example, the phrase "aging male doctor" contains two adjectives: aging and male. The phrase would make less sense if written, "the aging and male doctor."

That signals that these adjectives are cumulative. 

Always separate consecutive coordinate adjectives with commas. That's because coordinate adjectives are of equal importance to the noun they modify.

Unlike cumulative adjectives, you can separate coordinate adjectives with "and." 

For example, the phrase "yellow, rubber jacket" contains coordinate adjectives yellow and rubber.
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You could rewrite the sentence as "yellow and rubber jacket" or "rubber, yellow jacket" without scrambling the meaning. That's a sign that these adjectives are coordinate, and should be separated with commas. 

Parenthetical Expressions

Parenthetical expressions are words and phrases that you'd expect to see in parentheses. These words and phrases could be removed from the sentence without changing its meaning. 

Like modifying phrases, parenthetical can be essential or non-essential. You should always offset non-essential parenthetical with commas, parentheses, or em-dashes. 
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For example, "If you're wondering, yes, we are dating" is correct. "We are, of course, dating" is also correct. 

Indicating a Quote

Always indicate the start of a quote with a comma. For example, "She said, "I want to play soccer" is correct. 
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You don't have to offset paraphrased quotes with commas. For example, "She said she wants to play soccer" would be correct. 

Cities, States, and Countries or Dates, Ages, and Titles

There are certain nouns with which you must always use commas. For example, always separate cities, states, and countries with commas like this: "San Francisco, California, U.S.A."

You should also separate dates, ages, and titles with commas. For example:
  • "We set off on November 23, 2019."
  • "John Smith, age 92, placed first in the marathon last weekend."
  • "Jane Doe, CEO of The Best Company, gave the presentation."

For titles, keep in mind that there are instances where you don't need a comma.

​For example, if you're using the proper title (e.g., President Joe Biden), you don't need a comma. 

Separating the Same Word Used Consecutively in a Sentence

When writing copy in a conversational style, there are times when you may need to use a word consecutively in a sentence.

​For example, "The problem is, is there a reason to use a comma here?" 

Always use a comma to separate the same words used consecutively.  

The Oxford Comma Debate: Is it Really Necessary?

You may have discussed the Oxford Comma in ad school or when earning your copywriting certificate. But do you know why it's so important? 

As we've mentioned, the Oxford Comma is a comma used to offset the penultimate entry in a list, usually separated from the other items with "and." 
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If you ask us, copywriters should always use the Oxford Comma. The only exception to this rule is if your client's branding style guide forbids its use. 

Why Copywriters Should Use the Oxford Comma

Consider the sentence: "We're holding the meeting for our investors, naysayers and lobbying groups." The way we wrote this sentence alters the intended meaning, implying that the company's investors are naysayers and lobbyists. 

With the Oxford Comma, the sentence would read: "We're holding the meeting for investors, naysayers, and lobbying groups." This phrasing makes it clearer that three groups will attend the meeting. 

The Oxford Comma creates clarity and avoids misattributing adjectives to the first item in the list.

​That's why, unless your client requests otherwise, we recommend always offsetting the final word in a list with the Oxford Comma.

Take a Free Copywriting Grammar Review Course

Commas are essential for every copywriters' toolbox. They'll help improve sentence clarity and ensure you communicate your points the way you mean them.

​Using these ten rules for commas, you'll impress your advertising clients with professional copy every time. 

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