• Emma Lawson

Copyedit clinic: How to use commas for clarity

Updated: Aug 5


How and when should you use a comma? If you’ve asked yourself this question, you’re not alone. Commas are used often and often used incorrectly. This probably explains why the correct use of commas was the number one request in response to my last round of ‘copyedit clinic’ punctuation and grammar issues.

Surely, you can just use commas when you would take a natural pause in a sentence, right? Not quite. The true function of commas is to remove ambiguity by clarifying meaning and sense. Even the best writers trip up sometimes, so let’s take a brief tour of our misused little friend, the comma.

Here’s our sickly sample:

Tom, a twenty-something bachelor and Claire an English Literature student, first met at a mutual friend’s party. Claire remembered that day, clearly. She’d been one of the first to arrive. Tom arrived shortly after looking sharp in a classy shirt and tailored trousers. Damp with spilt drinks, he sat at a long thin table reading a book on Classical, Baroque architecture.

Sam leaned on the bar counter next to her. ‘Can I get you a drink Claire?’

‘Go on then. Cheers Sam. I’ll have a glass of Prosecco’ Claire replied.

Sam ordered four mojitos, two glasses of Prosecco and a vintage bottle of la Tâche Domaine de la Romanée-Conti.

Claire knocked back her Prosecco much too quickly, she wanted to ease her nerves.

Tom was walking straight towards her followed by two friends, a lanky-looking guy with jet black hair and a petite blonde.

Her stomach lurched. Men who seemed like a strange and foreign species, never approached her.

She and Tom spent the entire evening together. He walked her home and gave her a quick kiss on the cheek before saying goodnight.

Claire headed back to her room and sank onto her bed heavy with the scent of Tom’s aftershave.

How many comma errors did you spot? There are quite a few! Let’s break this down into common types of comma. We’ll begin with the number one offender.



Bracketing/isolating commas

When it comes to misuse, this type of comma is a common culprit. However, it’s simple to resolve. Take this sentence from our sample:

Tom, a twenty-something bachelor and Claire an English Literature student, first met at a mutual friend’s party. ❌

What is the essential information in this sentence, and what can be removed for it to still make sense? Here, we find that Tom meeting Claire at a mutual friend’s party is the essential information, and the other details are weak interruptions, which merely add information. If we take out the details about Tom’s bachelor status and Claire’s degree subject, the sentence still makes sense.

Tom and Claire first met at a mutual friend’s party.

This stands as a complete sentence. The removal of the bachelor and student parts of the sentence does not affect its essential meaning. Therefore, we can say they are non-restrictive (or non-defining) relative clauses. They add information but can be removed without destroying the meaning of the sentence.

A non-restrictive clause always needs a bracketing (or parenthetical) comma, and these are always set off in pairs unless they are at the beginning or end of a sentence.

Here is where the commas should be placed in our sample sentence:

Tom, a twenty-something bachelor, and Claire, an English Literature student, first met at a mutual friend’s party. ✅

Here’s another example:

Men who seemed like a strange and foreign species, never approached her. ❌

We need to be careful where we place commas in this sentence, because there are two possible meanings:

1) All men seem like strange and foreign species to her and never approach her

2) Only the men who seem like a strange and foreign species never approach her; other men do.

The placement of commas depends on the author’s intended meaning. If the first option is the intended meaning, then the sentence will be corrected by adding a comma after ‘men’:

Men, who seemed like a strange and foreign species, never approached her. ✅

This middle part of the sentence (‘who seemed like a strange and foreign species’)

needs to be paired off or bracketed with commas to show that it’s a non-restrictive clause, in that it doesn’t restrict the meaning of the sentence to particular men but refers to all men.

However, if the second intended meaning was the case, then we’d be referring to a restrictive clause, because the meaning is restricted to particular men. The problem would be solved by removing the comma:

Men who seemed like a strange and foreign species never approached her.

Another example of errant comma use in our sample sentences is this:

Claire remembered that day, clearly. ❌

The ‘clearly’ part of the sentence is an essential part of the sentence as opposed to a weak interruption; therefore, it should not be preceded with a comma. Commas should not be used to separate the basic parts of a sentence (subject and verb, verb and object).

Here’s another example of errant comma usage separating main clauses from weak interruptions/parenthetical asides:

Damp with spilt drinks, Tom sat at a long thin table reading a book on Baroque, architecture. ❌

Who is damp with spilt drinks, Tom or the table? Without a comma to clarify this, we’re left with a ‘dangling participle’ or ‘dangling modifier’ whereby parts of the sentence are modifying others in a confusing way.

Tom sat at a long, thin table, which was damp with spilt drinks, reading a book on Baroque architecture. ✅

Alternatively, this could be corrected as follows: ‘long, thin table damp with spilt drinks.’

Your computer grammar checks won’t pick up on dangling participles/modifiers, so you must keep an eye out for them! With practice, you’ll soon be a dangling participle pro!

Did you spot the other ambiguous sentence in desperate need of a correctly placed comma?

Claire headed back to her room and sank onto her bed heavy with the scent of Tom’s aftershave. ❌

If the author’s intended meaning is that Claire was heavy with the scent of Tom’s aftershave as opposed to the bed, the above sentence needs a comma after ‘bed’.

Claire headed back to her room and sank onto her bed, heavy with the scent of Tom’s aftershave. ✅

Well done if you got that one!


Vocative commas

A vocative comma should be used to address a specific person or persons.

‘Can I get you a drink Claire?’ ❌

‘Can I get you a drink, Claire?’ ✅

Cheers Sam. ❌

Cheers, Sam. ✅


Commas separating direct and quoted elements

Commas are used to separate direct speech or quoted elements from the rest of the sentence.

‘I’ll have a glass of Prosecco’ Claire replied. ❌

‘I’ll have a glass of Prosecco,’ Claire replied. ✅

Good choice, Claire. The exception to this rule is when another punctuation mark is used to separate the rest of the sentence, e.g. ‘I’ll have a glass of Prosecco!’ Claire replied.


Commas after conjunctions

Speaking of Prosecco, (I wouldn’t say no) did you notice the misused comma in this sentence?

Claire knocked back her Prosecco much too quickly, she wanted to ease her nerves. ❌

What’s happened here is an example of a ‘comma splice. A comma splice is where a comma is incorrectly used to join two clauses ­­– Claire drinking her Prosecco too quickly and wanting to subdue her nerves.

To correct this, you can do any of the following depending on how you want to influence the tone and flow of the sentence:

a) Split the clauses into two distinct sentences.

b) Insert a coordinating conjunction (but, and, yet, etc.), and add a comma before.

c) Use a colon (see this penultimate section of this post for info on colons).

a) Claire knocked back her Prosecco much too quickly. She wanted to ease her nerves. ✅

b) Claire knocked back her Prosecco much too quickly, but she wanted to ease her nerves. ✅

c) Claire knocked back her Prosecco much too quickly: she wanted to ease her nerves. ✅

Commas after introductory clauses

Commas can be used after introductory clauses to add clarity and remove ambiguity.

Take this sentence from our sample (if you can get past the clichéd description):

Tom arrived shortly after looking sharp in a classy shirt and tailored trousers. ❌

Did Tom arrive shortly after Claire or did he arrive shortly after Claire, having previously looked sharp in a classy shirt and tailored trousers?

A comma after ‘shortly after’ will remove the ambiguity:

Tom arrived shortly after, looking sharp in a classy shirt and tailored trousers. ✅


Listing commas

Commas are used to separate items in a list. How they’re used in lists is sometimes a cause of confusion. There are two types of things used in lists:

a) Qualitative or gradable things

b) Classifying things

The first require commas between them; the second do not.

he sat at a long thin table reading a book on Classical, Baroque architecture. ❌

he sat at a long, thin table reading a book on Classical Baroque architecture. ✅

Long and thin are gradable adjectives, but Classical Baroque architecture is a classifying description. You’ve got to wonder about a guy who goes to a party and reads a book about Classical Baroque architecture though...


Serial/Oxford commas

I know you’ve been waiting for the good old Oxford comma debate, so let’s get stuck in. In a nutshell, consistency is the thing to aim for, whatever your preference. An Oxford comma places a comma before the last ‘and’ in a list, e.g. ‘an apple, an orange, and a kiwi fruit’.

They are useful in resolving ambiguity in a sentence, but can also be used when the last item in a list is longer than the ones before it, e.g. Sam ordered four mojitos, two glasses of Prosecco, and a vintage bottle of la Tâche Domaine de la Romanée-Conti.

Sam knows how to party. Sam has money to blow. We all need a friend like Sam. But in terms of resolving ambiguity, what did you make of this sentence from our sample?

Tom was walking straight towards her followed by two friends, a lanky-looking guy with jet black hair and a petite blonde.

Did you think that Tom was followed by two friends and a lanky guy with jet black hair and a petite blonde? Or did you think that Tom had two friends with him: the lanky guy and the blonde?

An Oxford comma resolves the ambiguity if the author’s intended meaning is the first option.

Tom was walking straight towards her followed by two friends, a lanky-looking guy with jet black hair, and a petite blonde.


Summing up

  • Isolating/bracketing commas separate weaker interruptions/asides (non-restrictive relative clauses). They must be paired off unless at the beginning or end of a sentence. The main clause must make sense if you took away the non-restrictive relative clause.

  • Watch out for dangling participles/modifiers. Read back to yourself to see if what you’ve written really makes sense and place the comma accordingly.

  • Vocative commas are placed before a specific name/s when addressing a person/persons.

  • Commas separate direct speech or quoted elements.

  • Commas can be used after conjunctions.

  • Commas can be used after introductory clauses.

  • Commas are used to list adjectives or things.

  • Serial/Oxford commas need to be used consistently. They should be used when there is any ambiguity of meaning and are placed before the last ‘and’.

Have you got any other questions for the copyedit clinic series? Let's hear them! I’ve had LOTS of training, practice and experience to solve your thorny word problems.


If you’re pushed for time and need someone to tighten up your CV/cover letter, blog post, web copy, printed copy, article or book manuscript, get in touch! Drop me a message on my contact page. I’d be delighted to discuss it with you in more detail.

Say hello and join the conversation! You can find me on:

Twitter: @emmalawsonedits,

LinkedIn: @emma-lawson-edits

Instagram: @emmalawsonedits

Facebook: @emmalawsonedits