Those of us writing for the web are forever being told to use lists. But they have their place in books, too. Web readers aren’t the only ones with a tendency to skim. Pretty much any time you have a bunch of concepts to discuss, a list is useful.
☐ Lists are numbered when sequence is important, and bulleted if not.
Here’s an example from a wellness article I wrote. It’s typical of what I see in manuscripts. Here’s how the first draft might have looked:
In her great TED talk, “Why Dieting Doesn’t Usually Work,” neuroscientist Sandra Aamodt showed that the four most important healthy habits don’t directly include weight: eating plenty of fruits and vegetables, exercising three times a week, not smoking, and drinking in moderation.
Now there are only four items in that series. It’s perfectly readable. There’s nothing wrong with it. But in the final version, I presented it this way:
…the four most important healthy habits don’t directly include weight:
- Eating plenty of fruits and vegetables
- Exercising three times a week
- Not smoking
- Drinking in moderation
The bulleted list is not only easier to read, it’s also easier for the reader to find this information again, at least in a print edition, because it’s presented in a way that’s visually different from the surrounding text.
This list is a borderline case. It works either as a series (what The Chicago Manual of Style calls run-in,) or as a list (vertical). If the items in your series are very short, CMOS recommends using the run-in style, “especially if the introduction and the items form a complete grammatical sentence.”
When to Use a Semicolon
People like to use semicolons in run-in lists. But they are only needed if the items in the list contain commas. Here’s the example given by CMOS:
You are advised to pack the following items: (a) warm, sturdy outer clothing and enough underwear to last ten days; (b) two pairs of boots, two pairs of sneakers, and plenty of socks; and (c) three durable paperback novels.
Note that in this example the letters used to set apart the items in the list are fully enclosed in parentheses. We often see writers using just one, e.g., “plenty of socks; and c) three durable…” CMOS does not allow for a single parenthesis, either with numbers or letters.
Use Complete Sentences
Note also that the introductions to these lists are complete sentences. If you construct your introduction so that the list itself is a part of the sentence, then don’t separate it with a colon.
You are advised to pack warm, sturdy outer clothing and enough underwear to last ten days; two pairs of boots, two pairs of sneakers, and plenty of socks; and three durable paperback novels.
To get technical for a minute, the subject of the sentence is you, the verb is pack, and the items in the list are the objects. The object of the sentence should not be separated from the verb by a colon.
When the items in a list are not complete sentences, as in the bullet list above, they do not take periods. If each item were a complete sentence, then they would have periods at the ends.
Consider implementing these healthy habits:
- Eat plenty of fruits and vegetables.
- Exercise three times a week.
- Stop smoking.
- Drink in moderation.
Generally speaking, you’re going to use bullets more often than numbers. People are really fond of numbers because of the number-based “listicles” that are so prevalent on the web. And it’s true that if the list in your book has a subheading like “Four Important Health Habits,” you could make it a numbered list, to reinforce the numbering. But CMOS advises reserving numbers for instances when they serve a purpose, such as indicating the order in which tasks should be done, or to suggest the chronology or hierarchy of the items.
The items in your list should all be of the same grammatical form. In the first example above, all the items are gerunds—verbs with an ing suffix that function as nouns. If the third item were “Stop smoking,” the verb stop would be functioning as an imperative rather than a noun, and would disrupt the parallelism of the list.
CMOS sets no specific limits on the length of run-in lists, only advising that they are best for “short, simple lists.” If the list is long, or the items within the list are long, break it into a vertical list for ease of reading. There are no quantitative rules for this. If you’re not sure whether your list is too long to be run-in, try it both ways and see which way looks better to you.