You often use multiple adjectives to describe the same noun. Sometimes, a comma is necessary to separate adjectives; other times, it is not. Knowing when to apply commas between adjectives clarifies your writing. This distinction is determined by the type of adjective used. Consider the following when you struggle with whether to use a comma in this situation.
Coordinate adjectives are fairly easy to spot. These are adjectives that both precede AND modify the same noun. Consider the following:
In both of the above examples, the adjectives that precede the noun (products) both modify the noun. There are several ways you can check yourself to determine if the comma is necessary. Coordinate adjectives are interchangeable. The above examples are easily rewritten to read like this:
When you can exchange the adjectives and retain the meaning of the sentence, you are dealing with coordinate adjectives, and a comma is necessary. Simply checking if the word “and” can replace the comma and maintain the meaning of the sentence is another self-check you can perform.
Cumulative adjectives are trickier. While these adjectives directly precede the noun, they do not always modify the noun. The adjective directly before the noun modifies the noun, and the first adjective modifies the adjective that modifies the noun. Confused? Consider the following for clarification:
Both of the above examples contain cumulative adjectives. In the first example, blue modifies the word sheets and makes “blue sheets” a single unit. Light modifies “blue sheets,” deeming a comma unnecessary. In the second example, the same principle applies. Cupboard modifies the word knobs and makes “cupboard knobs” one unit. Pewter modifies “cupboard knobs,” and brushed modifies “pewter cupboard knobs.”
Unlike with coordinate adjectives, cumulative ones are not interchangeable. See what happens when the adjectives in the above examples are rearranged.
The meaning is changed in the first example. Instead of implying that the sheets are a light blue color, the sentence conveys that the blue sheets are light, as in not heavy. The second example simply makes no sense.
The “and” test that works on coordinate adjectives would also fail with cumulative adjectives, meaning the comma is omitted in those instances as well because the sentence would not make sense with the word “and” between the modifiers.
Putting your adjective strings through the simple tests outlined here is sure to help you determine whether a comma is necessary. Simply rearrange the adjectives in your head or say the string out loud to yourself injecting the word “and” to replace adjectives. If either or both of those tests fail by making a sentence confusing or unclear, a comma is unnecessary.