When Does ‘and’ Need a Comma?

“We’re judged by the way we write and speak,” I often say.

Jeff Rubin, who founded National Punctuation Day in 2004, agrees:

“People judge us by the way we present ourselves — how we act, how we look, how we speak and how we write. When we are professional in all of these areas, we get our feet in the door for our choice of college, scholarship, job, promotion or business deal. If you’re unprofessional in any of these areas, it can cost you.”

As National Punctuation Day approaches — Monday, Sept. 24 — I’m sharing what I’ve found online about which punctuation mark is misused most often.

The comma was mentioned time after time.

It’s no surprise. I have been saving examples of comma misuse, especially in sentences with conjunctions — the joiners and, but, for, or, nor, so, yet.

To understand when — and when not — to use a comma with a conjunction, let’s review simple, compound and complex sentences.

Simple Sentence

A simple sentence generally has a subject and a verb. It expresses a single thought and can stand on its own. It’s sometimes called an independent clause or a complete sentence.

Here are examples are simple sentences.

  • Sam smiled.
  • Sam decided to walk home.
  • Sam brushed his dog, Buster.

Compound Sentence

A compound sentence has two independent clauses. Each clause has a subject and a verb.

When you join two independent clauses (often with conjunctions and, but, for, or, nor, so, yet), you link them with a comma.

In these examples, each second independent clause is underlined.

  • Sam smiled, and his dog also seemed to be smiling.
  • Sam decided to walk home, but he took a detour along the beach.
  • Sam brushed Buster, yet he knew his pet really needed a bath.

Complex Sentence

A complex sentence includes an independent clause and at least one dependent clause. A dependent clause does not fully express an idea. It has a subject and verb, but it depends on other words for its meaning.

When you join an independent clause with a dependent clause, you do not need a comma between them.

In these examples, the dependent clauses are underlined. Note that the dependent clauses would not make sense if they stood alone.

  • Sam smiled as he brushed Buster.
  • Sam walked home along the beach while the sun was setting.
  • Sam brushed buster on the porch until all of the sand was gone.

Here are six real-world examples with an unnecessary comma.

My rewrites either:

  • delete the comma
  • add a subject, a verb — or both — to the second clause
  • replace the comma with a semicolon, or
  • break the clauses into two sentences

1) Police had not yet obtained surveillance video, but were following up on a few potential leads.

  • Police had not yet obtained surveillance video but were following up on a few potential leads.
  • Police had not yet obtained surveillance video, but they were following up on a few potential leads.

2) The ads are backed by significant statewide buys, and will run through the rest of July.

  • The ads are backed by significant statewide buys and will run through the rest of July.
  • The ads are backed by significant statewide buys, and they will run through the rest of July.

3) The European Union had warned of retaliatory charges last week, and outlined those plans on Wednesday.

  • The European Union had warned of retaliatory charges last week and outlined those plans on Wednesday.
  • 
The European Union had warned of retaliatory charges last week, and it outlined those plans on Wednesday.
  • The European Union had warned of retaliatory charges last week. It outlined those plans on Wednesday
.

4) For now, I have a wrist support on, and am on light duty.

  • For now, I have a wrist support on and am on light duty.
  • For now, I have a wrist support on, and I am on light duty.

5) Aretha Franklin was not only a powerhouse of a singer, but also a powerhouse when it came to slamming her critics.

  • 
Aretha Franklin was not only a powerhouse of a singer but also a powerhouse when it came to slamming her critics.
  • 
Aretha Franklin was not only a powerhouse of a singer; she was a powerhouse when it came to slamming her critics.

6) This is an exciting milestone, and shows major progress toward helping the state boost its clean economy.

  • This is an exciting milestone, and it shows major progress toward helping the state boost its clean economy.
  • This is an exciting milestone that shows major progress toward helping the state boost its clean economy.
  • This is an exciting milestone; it shows major progress toward helping the state boost its clean economy.

Note: The frequent use of a comma before and in the above examples suggests that some writers believe and always should be preceded by a comma. That is not the case.

These five examples are missing a comma. Each is made up of two independent clauses.

1) They took their language with them and today most languages in Europe and Western Asia share a common descent from that initial language

  • They took their language with them, and today most languages in Europe and Western Asia share a common descent from that initial language. 

2) This is a heartbreaking reminder of the split-second decisions that officers must make every day and it’s also a sobering reminder of the destruction that a lone individual with a handgun can create.

  • This is a heartbreaking reminder of the split-second decisions that officers must make every day, and it’s also a sobering reminder of the destruction that a lone individual with a handgun can create.

3) Cover letters have changed dramatically in the last few years and there are new rules about what makes them effective.

  • Cover letters have changed dramatically in the last few years, and there are new rules about what makes them effective.
  • Cover letters have changed dramatically in the last few years; there are new rules about what makes them effective.

4) But he couldn’t do that and his failure happened in real time for everyone to witness.

  • But he couldn’t do that, and his failure happened in real time for everyone to witness.

5) For the first time in history, the gender pay gap is at an all-time low and we’ve got more females heading companies than ever before.

  • 
For the first time in history, the gender pay gap is at an all-time low, and we’ve got more females heading companies than ever before.
  • For the first time in history, the gender pay gap is at an all-time low. We have more females heading companies than ever before.

You’ll find other explanations of comma use here.

Yes, we are judged by the way we write and speak. Commas separate certain elements of a sentence that tell us as readers or speakers when to pause. The pauses help make our messages clear.

Command your commas! Mastering grammar — the words you choose, how you string them together and how you punctuate them — will help you write and speak with authority and confidence.

Are you puzzled by punctuation or other elements of grammar? I welcome questions and comments, either in the comment section below or by email.

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Kathy Watson

Kathy Watson has a love/hate relationship with grammar; she loves words and the punctuation that helps them make sense, yet she hates those pesky rules. A self-proclaimed ruthless editor, she prefers standard usage guidelines of The Associated Press Stylebook. Her easy-to-use Grammar for People Who Hate Rules helps people write and speak with authority and confidence. She encourages and welcomes questions and comments. (Email)