When to use a comma: series and adjectives
This is the fourth and final article in the series on how to use a comma. In this article, we’ll talk about separating independent items in a series and independent adjectives with commas.
A series is simply a list of items in a sentence. The items are separated with commas, and the final item is connected with “and” or “or”—for example, “A transitional phrase creates a logical connection between phrases, clauses, or sentences.” If you’re wondering why there’s an extra comma before the conjunction “or”, it’s called the Oxford comma.
And when there are two or more independent adjectives in front of a noun, we separate them with commas—for example, “long, slow path” and “obvious, inescapable conclusion”. When I say “independent”, I mean that you can remove one of the adjectives without affecting the other. That is, in the first example, the path is long regardless of speed.
You can also have compound adjectives (e.g. fan-forced, light-green, high-risk, low-grade, open-ended) and adjectival phrases (just-in-time, day-to-day, black-and-white) that modify the following noun as a unit. In such cases, we connect the elements of the phrase with hyphens. For example, note the difference between a light-blue jacket and a light, blue jacket.
Finally, for completeness, I should also mention that the comma is used to format large numbers (e.g. 1,234,567), bibliographical references (e.g. Barton, Lien & Lunde [1974, fig. 8]), and post-nominals (e.g. Dr Joan de Wik, PhD[Geophys] UWA, FAusIMM), but not dates (e.g. 3 pm Tuesday 27 July 2021) nor bulleted (vertical) lists. We’ll revisit these in later articles, especially punctuating vertical lists and vertical sentences, which are often done incorrectly.
If you missed any of the other articles in this series on the comma, you’ll find them here:
Series (this article)
Adjectives (this article)
