When do you need a comma between adjectives?

Have you ever wondered when you need to use a comma between adjectives? Some adjectives should have a comma between them and others shouldn't. 

Why do we use a comma between the adjectives long and narrow in sentence two, but not between the adjectives three and furry in sentence one?

If you've ever Googled this question, you've probably landed on an article stating this rule: use a comma between coordinate adjectives.

That rule sounds simple, but it's a bit hard to apply because no one knows what a coordinate adjective is!

Let's untangle this one together. 

We walked down the long, narrow path.

Long and narrow are modifying the noun path independent of each other. Long is modifying path, and narrow is modifying path. 

If adjectives are coordinate, put a comma or the word and between them.

This lesson might not be very helpful yet, but stay with me because the magic is about to happen! One way to learn about what something is is to learn about what something isn't. So, our next question is As opposed to what? How else would an adjective modify a noun? 

Enter: cumulative adjectives

Three furry cats cuddled on my lap.

Although it might not seem like it, three and furry are modifying the noun cats differently. Furry is modifying just the noun cats, and three is modifying the phrase furry cats. 

If adjectives are cumulative, don't put a comma between them. That would break up their cumulative effect!

It's not always easy to identify adjectives as coordinate or cumulative, but there are two tests that we can apply in order to help us figure it out.

If you can't tell whether your adjectives are coordinate or cumulative, try putting and between them. If your sentence sounds normal, you have coordinate adjectives, and they need a comma between them. If your sentence sounds strange, you have cumulative adjectives, and you shouldn't use a comma.

Three and furry cats cuddled on my lap. --> No

This doesn't sound good. Three and furry are cumulative adjectives. They shouldn't have a comma between them.

Three furry cats cuddled on my lap. --> Yes

Let's apply this test to our other example sentence.

We walked down the long and narrow path. --> Yes

This sounds good. These are coordinate adjectives, and we should use a comma or the word and between them.

We walked down the long, narrow path. --> Yes

Try reversing the order of the adjectives. If the sentence still sounds normal, then you have coordinate adjectives, and they need a comma between them. If your sentence sounds strange, then you have cumulative adjectives, and you shouldn't use a comma. 

Furry three cats cuddled on my lap. --> No

This doesn't sound normal. These are cumulative adjectives, so there shouldn't be a comma between them.

Three furry cats cuddled on my lap. --> Yes

Let's apply this test to our second example sentence.

We walked down the narrow, long path. --> Yes

This still sounds okay. These are coordinate adjectives, and there should be a comma between them.

We walked down the long, narrow path. --> Yes

You know that I love diagramming sentences, so you might be wondering if diagramming these adjectives will help you figure out if they are coordinate or cumulative.

As you can see, all of the adjectives are diagrammed in the same way. Unfortunately, one limitation of sentence diagramming is that, although these adjectives function differently, we diagram them in the same way, so diagramming these sentences won't help you figure out whether or not you need a comma. 

Whew! You made it with me all the way to the bottom of the page! Since you had the tenacity to read through this whole lesson, I think that you deserve a gold star. This is for you.