If you’ve ever had trouble using the colon in your text, you are not alone. I often encounter mistakes in colon use during copy editing and proofreading. This post contains information on how to properly use the colon to polish and clarify your writing.

Here I divide the job of the colon into two categories: formatting and introducing.

Most writers are familiar or confident when using the colon to format. Colon use for formatting can be dependent on your style guide or field, so make sure you always check the guide or field conventions. Here’s a list of how the colon is commonly used in formatting:
Time

1. 3:45 pm (time of day)
2. 04:25:02 (hrs:min:sec)

Ratios

1. 1:1 (a one-to-one mixture)
2. v:v (a volume-to-volume mixture)

Formal address
    Dear Dr Smith:
Books of the Bible

1. Matthew 1:3
2. Genesis 2:15

Below are examples of colon use in two different academic fields.

The American Medical Association uses the colon in references between the issue number and page numbers.
Author(s), Article title. Abbreviated Journal Name. Year;vol(issue No.):inclusive pages. DOI

The Council of Science Editors uses the colon in titles and subtitles (with the caveat that the period can also be used—check the style guide!)

Scientific  Style and Format: The CSE Manual for Authors, Editors, and Publishers

Always double check the conventions in your field when you use the colon for formatting!

“We used three techniques to characterize the product: NMR spectroscopy, mass spectrometry, and elemental analysis.”

The above example has a complete independent clause before the colon; the list of items following the colon clarifies the idea by listing the techniques used. To check if this is correct, separate the information into more than one sentence.

“We used three techniques to characterize the product. They were NMR spectroscopy, mass spectrometry, and elemental analysis.”

Although both versions are correct, the colon can combine these sentences into one, thereby improving the flow of the text.

Here’s an incorrect version that has an incomplete clause before the colon, where a preposition is separated from its direct objects by a colon.

“We characterized the product by: NMR spectroscopy, mass spectrometry, and elemental analysis.”

If you check this with a period you get, “We characterized the product by.” This is an incomplete sentence! Wrong!

The use of colons to enumerate lists can be tricky when the words “including” and “the following” are used.

Incorrect: “We used multiple techniques to characterize the product, including: NMR spectroscopy, mass spectrometry, and elemental analysis.”

Correct: “We used multiple techniques to characterize the product, including NMR spectroscopy, mass spectrometry, and elemental analysis.”

The colon is not used when “including” is present even though it indicates a list to follow. But, the colon is used when “the following” or “as follows” is present.

“We characterized the product with the following techniques: NMR spectroscopy, mass spectrometry, and elemental analysis.”

The colon can also be used for lists that aren’t in-line with the text (as I showed above). The next time you need to present an in-line list, try using a colon!

So far, I’ve given examples where I use a colon to introduce an in-line list or series to clarify the idea before the colon, but the colon can introduce a phrase, a complete sentence, a long quote, or, as in the sciences, equations.

“Pressure, volume, and temperature are related by the ideal gas law: PV = nRT”

“Einstein’s most famous equation relates energy, mass, and the speed of light:
E = mc2,
where E = energy, m = mass, and c is the speed of light.”

Notice that the punctuation in the dependent clause after the colon follows normal grammar rules.

Here’s an example where the colon introduces another sentence.

“The colon is a powerful punctuation mark: a variety of informative statements can be introduced by the colon.”

Making the initial letter after the colon upper or lower case will ultimately be determined by the style guide you are using and conventions of your field, but here are some basic tips.

For items in a list, if the listed items are themselves complete sentences, use a capital letter after the colon and for each item. If the listed items are not complete sentences, make the initial letter lowercase. However, if there is only one sentence after the colon, you may need to keep the initial letter lowercase—check your style guide!

Items presented in an in-line list can be separated by commas, semicolons, or periods. Use periods for sentences; semicolons when the item has commas within it; and commas for non-sentences. Whichever you choose, the punctuation must be consistent within the list.

For displayed lists, semicolons and commas aren’t used between items. Periods are only used when the items themselves are sentences. Closing punctuation is not always required after the final item in a displayed list—again, check your style guide!

Numbers, enclosed by parentheses, may be used. This will depend on how you want to present the information. For example, if you are writing a grant application and a certain number of specific aims are required, you may want to number these aims in your list. Check the author guidelines!

Just like any other skill, using the colon correctly in writing takes practice. When used correctly, the colon can improve the precision, clarity, and flow of your text.

How do you feel about using the colon? Leave a comment and we can chat!

As a copy editor, one of the most common punctuation mistakes I encounter in STEM writing is the use of a hyphen when an en dash is needed. Do you know how to correctly use the en dash in scientific writing? Read on to learn how and when to use this misunderstood punctuation mark.

Can you pick out the en dash from the picture? Here’s a hint: longer than a hyphen, but shorter than the em dash.  And not to be confused with the minus sign. Common knowledge says that the en dash is so named because it is the approximate width of “N”. However, the name origin is more complicated. As described by Matthew Butterick in hyphens and dashes, “em and en refer to units of typographic measurement, not to the letters M and N.”

According to the Chicago Manual of Style (CMOS), the authoritative style guide for writers and editors that I describe here,
"Hyphens and the various dashes all have their specific appearance…and uses…. The hyphen, the en dash, and the em dash are the most commonly used. Though the differences can sometimes be subtle—especially in the case of an en dash versus a hyphen—correct use of the different types is a sign of editorial precision and care."

In UK English style the en dash with space before and after replaces the em dash, but this use of the en dash won’t be discussed further because it is atypical in US English style.

Recently, when I wanted to reviewing the rules on en dash usage in science writing, I grabbed my copy of the “Best Punctuation Book, Period” by June Casagrande. I love this book. It is very readable and easily searchable. Casagrande has a section for each punctuation mark, which includes a Punctuation Panel’s, made up of professional copy editors in news media and book publishing, preferred usage of the mark. As expected, the chapter on the en dash is quite short. However, I did a double take when I read, “The en dash…applies solely to book style. It does not exist in news, science, or academic style.” WRONG!
The en dash has very specific uses in STEM writing.
The en dash is used to

• improve clarity of compound adjectives
  
• indicate equal contribution
• indicate numerical ranges
• indicate chemical bonds
  

Both CMOS and the American Medical Association (AMA) Manual of Style 11th edition prescribe use of the en dash when the compound adjective has an open element or already-hyphenated element. This helps avoid ambiguity.

For example:
From CMOS, Chuck Berry–style lyrics (here, the name “Chuck Berry” is a known open unit, but it is a compound adjective with “style”)

From the AMA, non–English-language journals

When a compound adjective has two components that have equal weight, the en dash is used. The American Chemical Society (ACS) and the American Psychological Association both describe this usage, known as the peer en dash. This includes collaborators of scientific findings or joint authorships.
Here are examples.

• Diels–Alder reaction
• Beer–Lamber law
• Test–retest reliability
• Structure–activity relationship
  

Another use of the en dash is to indicate inclusive numerical ranges (no spaces before or after the en dash). Use it for dates, times, data, and so on.

“The graph shows the mean of the data from multiple biological replicates (n = 3–6).”

However, don’t use the en dash when “from” precedes the range—the word “to” is used instead.

“Participation in the study was measured from May 2010 to April 2012.”

Furthermore, if one of the numbers is negative, then the en dash should not be used.

“Over the last week, temperatures were −10 to 23 °F.” Not “−10–23 °F”.

Follow your style guide of choice to determine if units need to be repeated within numerical ranges. Of note, the AMA style guide 11th edition uses hyphens for numerical ranges. WEIRD!

Perhaps my favorite use of the en dash is in the chemical bond as prescribed by ACS. This is near and dear to my heart as I spent 6+ years working in chemistry and chemical biology. Here the en dash indicates a single covalent sigma bond.

H3C–OH
R2C–C(H)=O

Notice that the equal sign (same width as the en dash) denotes a double covalent pi bond.

The en dash has specific uses in science, and it’s important for clarity, formality, and professionalism to understand the different uses. Although CMOS recommends using other punctuation instead of the en dash or completely recasting the sentence, I suggest using the en dash without reservation. What do you think?

Have you ever almost used a semicolon, but abandoned the idea for fear of doing it wrong?

Or do you avoid semicolons because you worry they make your writing seem too stuffy?
If so, you aren’t alone.

Throughout modern history, semicolons have been one of the most misunderstood and polarizing punctuation marks in existence. For this reason, many writers shy away from using them altogether.

There are strong opinions about the semicolon’s use. Some writers and editors believe it makes things too choppy. Others believe a comma and coordinating conjunction do the same job. Still others fear it makes their writing seem elitist.

In this post, I’m coming to the defense of the semicolon. Get ready to learn more about what it is, how it is used, and why as an editor I use it often in my work.

According to Amy Einsohn’s and Marilyn Schwartz’s authoritative text The Copyeditor’s Handbook, the semicolon can act as a strong comma or a weak period.

Most style manuals agree that the semicolon has three jobs:

1. To join two related independent clauses without using coordinating conjunctions
2. To precede a conjunctive adverb when linking independent clauses
3. To separate complicated items in lists where commas are already used.

Semicolons can also be used to delineate items in references, but since reference formatting is not text writing, we won’t give into that here. However, if you’d like to learn more the University of Pittsburg Library system has a fantastic resource.

Let’s break down each of those three uses with some examples.

An independent clause is a clause that contains a subject and predicate that can stand alone, that is, it’s a complete sentence. Two related independent clauses have a logical connection to each other. With commas, a coordinating conjunction (“and”, “but”, “yet”) is needed to join two independent clauses. The short pause of the comma and the coordinating conjunction confirm that these ideas are related, but the comma may seem too hurried or trivializing. The long pause of a period may separate the ideas too much, thereby undermining some of the logical connection. The semicolon provides a middle ground for the pause—still evidencing the connection but allowing more space.

Semicolons are also required when conjunctive adverbs (“however”, “therefore”, “indeed”, etc.) are used to combine two independent clauses. Adverbs qualify and describe verbs, adjectives, other adverbs, and even sentences. If one independent clause emphasizes or scrutinizes another independent clause, a conjunctive adverb preceded by a semicolon can be used to show this relationship between the clauses.

For example: “We aimed to create ideal conditions for the desired reaction; however, we still identified by-products in the batch.”

Here, “however” emphasizes that we did our best to optimize and understand the reaction conditions. The substitution of “however” with “but” would emphasize the subsequent clause more.

If you list a series of items and one or more of the items has a comma, separating those items with commas may confuse your reader. Thus, a semicolon is warranted in this situation to separate the parts of the list.

“I’ve lived in Baltimore, Md; Tampa, Fl; and San Antonio, Tx.” Here a comma is conventionally used between the city and state so a semicolon should be used for clarity.

“We optimized the reaction’s reagents; additives, bases to act as hydrogen ion scavengers; duration; and temperature.” I specify the type of additive and its function. But the meaning would be different if commas were used: “We optimized the reaction’s reagents, additives, bases to act as hydrogen ion scavengers, duration, and temperature.” This suggests that additives and bases were needed.  

The jobs of a semicolon are straightforward. Still there are many people who find them frivolous or worse:

“If you have to use a semicolon, you didn’t write the sentence well enough,”—Personal communication.

“All they do is show you’ve been to college,”—Kurt Vonnegut Jr.

“They are more powerful more imposing more pretentious than a comma but they are a comma all the same. They really have within them deeply within them fundamentally within them the comma nature,” —Gertrude Stein.

One argument against the semicolon is that a comma or period can do the same thing. Furthermore, because it gives a slightly longer pause than a comma, it may seem too strong or abrupt in some contexts. On the other hand, it is a shorter pause than a period and may seem too weak.

,Personally, I think the semicolon has a place in a writer’s toolbox.

First, a semicolon can quickly fix comma splices, where two related—but independent—ideas have been joined with a comma. A semicolon can be swapped for that comma, making the sentence grammatically correct and retaining the intended pause and relationship.

Second, and perhaps more importantly, semicolons help vary sentence length. As discussed in The Copyeditor’s Handbook, a writer can control the audience’s attention by varying sentence length. Too many short independent clauses ending in a period can give the writing a choppy feel. This choppiness leads to reader fatigue. In contrast, sentences that are too long can be confusing and unclear, leading to disinterest; therefore, intentional use of the semicolon helps retain the reader’s interest.

Semicolon advocate Arthur Plotnik asserts in his book Spunk & Bite, “With a semicolon, there is a split-second of tease. . . . Semicolons inject expectation into sentences, and in literature expectancy is a good thing; it creates subliminal tension followed by release: the quiet ah’ of art.”

Here is an example Plotkin’s idea in action.

Take this sentence:
“It was a dark and gloomy morning, and the houses almost disappeared as I walked past.”
Although the sentence is technically correct, it lacks tension. But if we edit it to read as follows, much changes: “It was a dark and gloomy morning; the houses almost disappeared as I walked past.”

The semicolon adds tension and begs the question, “where were you going?”.

Whether you are a new writer or a seasoned one, it’s time to embrace the semicolon and use it to strengthen your writing.

Remember, semicolons can
1. provide longer pauses than commas and shorter pauses than periods
2. delineate relationships between related independent clauses
3. separate items in a complex list
4. add tension and interest to the text

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