Writers are often confused about whether to punctuate a phrase that includes two or more adjectives. To determine whether a comma is required between any two adjectives, test whether they are coordinate or noncoordinate.
Coordinate adjectives have equal status: They both modify a noun or noun phrase. By contrast, noncoordinate adjectives have different functions: The former type of adjective modifies a noun or noun phrase, and the latter modifies a phrase consisting of another adjective and a noun or a noun phrase when that other adjective is an essential description of the thing being described. The following sentences, and the discussions and revisions that follow, illustrate this point.
1. For decades, companies have assigned repetitive, manual tasks to robots.
Repetitive describes a type of manual tasks—it does not have equal status with manual in modifying tasks—so the adjectives are noncoordinate and no comma should follow the word: “For decades, companies have assigned repetitive manual tasks to robots.”
2. The 218-acre, oceanfront estate is for sale.
The phrasal adjective “218-acre” modifies “oceanfront estate,” not just estate, so the adjectives are noncoordinate and no commas are required: “The 218-acre oceanfront estate is for sale.”
3. A holistic forward-looking, risk-focused, continuous-monitoring approach is often difficult.
Forward-looking and risk-focused both describe “continuous-monitoring approach,” and they’re interchangeable, so they are coordinate adjectives and should be separated from each other by a comma. However, “continuous-monitoring” is not equivalent to the other phrases; it is an essential part of the phrase they are modifying, so the final comma is incorrect: “A holistic forward-looking, risk-focused continuous-monitoring approach is often difficult.” (Also, holistic modifies everything that follows, so it is noncoordinate and therefore no comma should follow it.)
4. Recognizing how a home meets your needs, and the needs of your family, can help you contribute to the development of a happy, healthy, home environment.
Home is not equivalent to happy and healthy, it is an intrinsic term describing the type of environment that can be happy and healthy. Those words, which are interchangeable, modify the phrase “home environment,” so the final comma is incorrect: “Recognizing how a home meets your needs, and the needs of your family, can help you contribute to the development of a happy, healthy home environment.”
5. The risks presented by this complex, fragmented, legacy architecture are rarely, if ever, considered.
Complex and fragmented describe “legacy architecture,” so legacy is not equivalent to the first two words and should not be separated from them. Those words, however, are interchangeable and must be set off by a comma: “The risks presented by this complex, fragmented legacy architecture are rarely, if ever, considered.”