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When to Place a Comma between Prenominal Modifiers

Copyediting (McMurry, 2011)

You may have heard the prescription that two adjectives falling before a noun should be separated by a comma. In fact, the behavior of prenominal (preceding-the-noun) modifiers is far subtler than this rule suggests. According to current style and usage guides, answering the following questions can help a copyeditor decide whether to place a comma between two prenominal modifiers: Is the modifier an adjective, a determiner, or a modifying noun? Is it coordinate or cumulative? Is the meaning it conveys subjective or objective?

While we sometimes place a comma between adjectives, we do not usually place a comma between adjectivals of different form classes (which are roughly equivalent to parts of speech). The term adjectival connotes a functional category describing any structure that modifies a noun. The term adjective conveys a specific form class. Structures from any number of form classes, including determiners, adjectives, and modifying nouns, might behave adjectivally. In other words, non-adjectives sometimes act like adjectives, modifying the head noun.

Let’s take a broad look at the order in which adjectivals fall before a noun. Martha Kolln and Robert Funk’s Understanding English Grammar gives the following order, organizing adjectivals by class: determiner | adjective | noun | headword. Determiners include articles (the, a), possessive nouns/pronouns (Sally’s, her), demonstrative pronouns (this, that), and numbers (one, sixth). We do not place a comma between a determiner and an adjective because these are adjectivals of different classes. For the same reason, a comma will not fall between an adjective and a modifying noun.

To better understand modifying nouns, we can study the example lead paint. Paint is the head noun, and lead describes it, so clearly lead is an adjectival. But is it an adjective?

One way to answer such questions is to perform a form class test. The test will produce either a marked (^) or an unmarked result. If you are fluent in standard written English and the sentence sounds even slightly unnatural to you, consider it marked. If it sounds natural, consider it unmarked. Be sure to listen for syntax as opposed to meaning. A bizarre meaning does not mean that the sentence is marked.

Since we are working within a descriptive grammar as opposed to a prescriptive grammar, test results are subjective and not always conclusive. The following tests, provided by Michael Haley, PhD, of the University of Alaska, have yielded clear results in my experience. Apply these to distinguish an adjective from a modifying noun:

Noun test: _______ can be a pain in the neck.
Adjective test: They are very _______.

The sentence will sound unmarked if the word you are testing is the proper form class for either test. Applying the tests to our example yields the following results:

Lead can be a pain in the neck.
They are very *lead.

Lead fails the adjective test and passes the noun test, so in the context of the sequence lead paint, it must be a modifying noun—a noun functioning like an adjective. Do not place a comma before or after it. Place the modifying noun directly before the noun it modifies, with any adjectives falling before the modifying noun.

Here are some marked and unmarked constructions illustrating the rule:

^Dobby played with red, lead paint.
^Dobby chose an ugly, revolting, lead paint.
Dobby played with red lead paint.
Dobby chose an ugly, revolting lead paint to play with.

Note the comma between ugly and revolting in the unmarked sentence. A comma falls between these modifiers because they are both coordinate adjectives. According to the Chicago Manual of Style, Understanding English Grammar, and Amy Einsohn’s The Copyeditor’s Handbook, coordinate modifiers take a comma between them, whereas cumulative modifiers do not. Kolln and Funk define a coordinate modifier as one that “describes the noun independently,” whereas a cumulative modifier “describes the combination of the next modifier plus the noun it modifies.”

To understand cumulative modifiers, imagine a Newton’s pendulum with the pendulum ball on the far right representing the head noun and each of the pendulum balls to its left representing a cumulative modifier. Say you have two cumulative modifiers—old and red—and a compound head noun, baseball cap. The kinetics of the sentence operate like the first swing of a Newton’s pendulum, where the pendulum ball old strikes red and conducts its energy through its neighbor. By the time the energy of that first strike reaches baseball cap, it has moved through red. For cumulative modifiers to do their job, they need to be touching, just like their counterparts in a Newton’s pendulum. Placing a comma between them disrupts a sentence’s kinetics.

By contrast, coordinate modifiers leap over everything between them and the head noun, striking the headword directly. Here are two tests to determine whether adjacent adjectives are coordinate:

Conjunction test: Does placing and between them sound natural? If so, this is evidence that they are coordinate.
Order test: Does the order of the adjectives seem to matter? If you can switch the order of the modifiers without producing a marked construction, this is further evidence that they are coordinate.

Applying these tests to the example above and the case of the gorgeous, friendly spy, I get the following marked and unmarked sentences:

The gorgeous and friendly spy said hello.
The friendly, gorgeous spy said hello.
^The old and red baseball cap sat on my bookshelf.
^The red old baseball cap was my favorite hat.

To my ear, the tests yield fairly clear results. Gorgeous and friendly are coordinate, whereas old and red are cumulative. We are not always so lucky, however, to have clear test results. Factors such as rhythm and idiom can complicate judgments based on native intuition.

Since we are operating within a descriptive rather than a prescriptive approach, there is no such thing as a false result from these tests. You might find that your native intuition clashes with that of another speaker—or even with the majority of speakers—in your milieu. If this happens, you may or may not choose to retrain your ear. Because the results of any one test are not always conclusive, it is best to apply at least two tests whenever possible. Weigh all the evidence you can obtain and make a judgment call.

One principle that will aid your evaluation of test results is that exceptions do not disprove the rule. You might ask, for example, what is wrong with saying the red old baseball cap, especially if there are two old baseball caps and you want to specify which one. In the right context, this might constitute an exceptional case. However, the goal of the test is to ascertain what sounds most natural most of the time. Therefore, the best question to pose is not what is wrong with saying…? but rather what sounds more marked? Even in the exceptional case above, it sounds a bit marked to me to switch the received order of our cumulative modifiers.

A better understanding of why tests work will aid a copyeditor’s decision-making process. For example, the order test works because, unlike coordinate modifiers, cumulative modifiers usually follow a fixed order based on meaning. According to Kolln and Funk, that order is size, shape, condition or age, color, and origin or material.

Adjective order in the case of the old red baseball cap follows this pattern. Old (age) falls before red (color). This deeply embedded rule of native syntax can provide further evidence when the basic tests prove inconclusive. If the modifier refers to size, shape, condition, age, color, origin, or material, chances are it is cumulative.

As the ordering of cumulative adjectives demonstrates, an examination of meaning can complement a grammatical approach based on form and function. The vocal pause indicated by a comma creates a slight break, helping us differentiate adjectives that fall into the same category of meaning. When you encounter two prenominal modifiers, consider whether their meanings are objective or subjective. A comma may be required between two subjective or two objective modifiers, but it is not needed between a subjective and an objective modifier.

Refashioning an example from Kolln and Funk, let us consider the case of the lazy green alligator. The adjectives lazy and green fall into distinct categories of meaning. Lazy is a subjective judgment, an abstract quality that might easily change depending on the speaker’s point of view. Green is a concrete, permanent quality that would not easily change based on the speaker’s perspective. Therefore, these two adjectives self-differentiate, and no comma is needed. In fact, placing a comma between them results in a slightly marked construction:

Kermit greeted the lazy green alligator.
^Kermit greeted the lazy, green alligator.

To my ear, the conjunction and order tests back up this judgment:

^Kermit greeted the lazy and green alligator.
^Kermit greeted the green lazy alligator.

Since these sentences are marked, I conclude that lazy is a coordinate adjective, whereas green is cumulative.

You may notice that cumulative modifiers also happen to be concrete and relatively permanent—they describe size, shape, condition, age, color, origin, and material. Coordinate modifiers tend to be subjective, changeable, and abstract. Categories of meaning seem linked to the designation of coordinate or cumulative adjectives, though not all objective modifiers are also cumulative.

Even armed with all these tools, you may encounter practical cases that defy a tidy understanding. Note that in the lazy green alligator, the cumulative adjective is a color, which sits quite close to the head noun in our ordering pattern for cumulative modifiers. This close proximity implies a tight relationship to the noun. What if we were to choose a different type of cumulative adjective, one that tends to fall farther away from the head noun, such as round? If we add a comma, can we switch the received order of coordinate and cumulative modifiers without creating a marked construction?

What sounds marked, judging by your native intuition and the tools introduced here?

Kermit greeted the lazy round alligator.
Kermit greeted the lazy, round alligator.
Kermit greeted the round lazy alligator.
Kermit greeted the round, lazy alligator.

To my ear, the third sentence sounds marked without the comma, and the first is slightly preferable to the second when one applies the conjunction test (^lazy and round alligator). Applying the conjunction test to the fourth sentence, I do not find it marked (round and lazy alligator). I conclude that both the first and fourth sentences are acceptable, the first being slightly preferable. How interesting that we could switch the order of coordinated modifier | cumulative modifier | headword with the addition of a comma when the cumulative modifier is a shape.

We can’t get away with this kind of switch without producing a noticeably marked construction when the cumulative modifier is a color.

^Kermit greeted the green lazy alligator.
^Kermit greeted the green, lazy alligator.

Although the second sentence grates on my ear less than the first, I can’t read either of these sentences without thinking how preferable it would be to switch the order of the adjectives, a judgment that conforms to Kolln and Funk’s statement, “Any coordinate modifiers will precede the cumulative modifiers in the string.” But when the cumulative adjective is a shape? Both variations sound fine to me as long as the round, lazy version contains a comma. This could imply that a cumulative shape modifier is somehow less cumulative and more coordinate than a cumulative color modifier.

Language is fluid, and judgments based solely on your ear as a fluent English speaker are valid, if not conclusive. Modern linguists strive to describe tendencies in the speech patterns of native speakers, rather than prescribe, judge, and generally tell a confident speaker that she is doing it all wrong. As a copyeditor, I walk this tightrope of descriptive grammar every day. If I encounter a marked construction resulting from a comma being placed between a determiner and an adjective, a coordinate and a cumulative modifier, two cumulative modifiers, or an adjective and a modifying noun, I will remove the comma. But when a case falls in the grey area or I sense I have reached the limits of my understanding, I fall back on a wise adage: when in doubt, don’t change it; let the author’s judgment stand.