To Comma or Not to Comma? When to put commas before “and”, “but”, “or”, “nor”, and “yet” made simple

Do you want to write clear sentences that use grammar and punctuation correctly? But do phrases like “compound predicate” and “subordinate conjunction” leave your mind blank? If that’s you, I’d like to help. In this blog series, I’m going to present the rules of grammar and punctuation without any jargon and with a heap of examples. 

Right, without further ado, let’s jump into one of the most common punctuation problems.

You’ve got a sentence with a joining word in the middle: and, but, or, nor, yet. And you don’t know if you should put a comma in front of the joining word.

Should it be: Tom shouted but Rachel did not come.

Or: Tom shouted, but Rachel did not come.

Here’s how you can know. Just delete the joining word and replace the comma with a full stop (or period). Like this: Tom shouted. Rachel did not come.

Then, ask this simple question: Are both of those sentences complete? 

Tom shouted. Yes, that’s a complete sentence. It’s a full piece of information or, we could say, a complete thought.

Rachel did not come. Yes, that’s complete, too.

We split the sentence in half, and both halves made complete sentences on their own. 

Here’s the rule: 

Place a comma before the joining word if both halves make complete sentences.

Therefore, we should add a comma before the joining word.

Tom shouted, but Rachel did not come. That’s perfect!

How about this sentence?

Steve drove to the shop, and bought six carrots.

Let’s delete the joining word and replace the comma with a full stop (period).

Steve drove to the shop. Bought six carrots.

Are both of those sentences complete?

Steve drove to the shop. Yes.

Bought six carrots. No. These words couldn’t stand on their own. We’d have no idea who bought the carrots.

We split this sentence, and only one half made a complete sentence on its own.

Now, remember: Place a comma before the joining word if both halves make complete sentences.

Therefore, we should not add a comma.

Steve drove to the shop and bought six carrots. Perfect!

Alright, let’s look at some more examples.

The road stretched on for miles, yet every mile was a pleasure to drive.

The road stretched on for miles. Every mile was a pleasure to drive.

Are both of those sentences complete? Yes.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? Yes.

In the autumn, leaves turn from green to gold and tumble to the ground like soft rain.

In the autumn, leaves turn from green to gold. Tumble to the ground like soft rain.

Are both of those sentences complete? No.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? No.

The books on the bookshelf hadn’t been read in years, yet they were treasured no less than when they were new.

The books on the bookshelf hadn’t been read in years. They were treasured no less than when they were new.

Are both of those sentences complete? Yes.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? Yes.

Alright, let’s take a breather because you might have a big WHY:

“Why does this rule instruct me to add a comma when both halves make complete sentences?” Well, complete sentences are not only capable of standing on their own, but they should stand on their own. Something must separate them. When two complete sentences sit together with a joining word between them, a comma does that necessary task of separation.

And back to some more examples:

Science fiction and fantasy are commonly abbreviated SFF, but if someone doesn’t know that term, they may be confused by it.

Science fiction and fantasy are commonly abbreviated SFF. If someone doesn’t know that term, they may be confused by it.

Are both of those sentences complete? Yes.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? Yes.

Computers can sometimes be helpful and complicated at the same time.

Computers can sometimes be helpful. Complicated at the same time.

Are both of those sentences complete? No.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? No.

I have a pair of sunglasses and a sunhat which often falls off my head.

I have a pair of sunglasses. A sunhat which often falls off my head.

Are both of those sentences complete? No.

Place a comma before the joining word if both halves make complete sentences.

Should there be a comma? No.

Alright, let’s take another breather and remind ourselves exactly what we’re doing.

First, we take a sentence with a joining word in the middle: and, but, or, nor, yet.

Second, we delete the joining word and insert a full stop (period) to create two sentences.

Third, we ask: Do both those halves make complete sentences on their own? 

Finally, we obey this rule: Place a comma before the joining word if both halves make complete sentences.

If you’re ready to keep the method in your memory, let’s head back to examples.

Happiness is precious, and joy is wonderful.

Happiness is precious. Joy is wonderful.

Should there be a comma? Yes.

You can have raspberry ice cream with a wafer or strawberry ice cream with chocolate sauce.

You can have raspberry ice cream with a wafer. Strawberry ice cream with chocolate sauce.

Should there be a comma? No.

Let me know if you’d like to come, but you don’t have to say anything if you’d like to stay.

Let me know if you’d like to come. You don’t have to say anything if you’d like to stay.

Should there be a comma? Yes.

You haven’t included any questions in your examples, but does this rule apply to them, too?

You haven’t included any questions in your example. Does this rule apply to them, too?

Should there be a comma? Yes.

The rule applies to questions and statements in the same way.

The rule applies to questions. Statements in the same way.

Should there be a comma? No.

This is the last example, but I hope everything is clear now.

This is the last example. I hope everything is clear now.

Should there be a comma? Yes.

That’s it. It’s really no more tricky than that. 

Now, I don’t expect you to go through everything you’ve written, deleting the joining words and adding full stops (periods). Maybe you’d like to do that to begin with, but very soon, this process should occur in your imagination. In my head, both of these are almost instinct: 

“Do both halves make complete sentences on their own?” 

and

Place a comma before the joining word if both halves make complete sentences.  

That’s why I recommend them: I believe they’re easy to memorise.

I’ll be watching the comments section, ready to answer any questions you have.

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