As we enjoy (or suffer through) the last remnants of winter here in the Northern Hemisphere, we thought we’d answer this excellent question from one of our clients:
“Why did you make this change? What is the difference between “-” and “–”?”.
In science writing, authors need to contend with three dashes: hyphen (-), en dash (–), and em dash (—), plus the minus sign (–). The size of these dashes varies, but they all have this in common: there are no spaces on either side of these punctuation marks; they are directly connected to the words they join. Here, we describe the correct usage of each of these pesky little horizontal lines in turn.
Hyphen: The shortest of the three dashes, the hyphen, is used to form compound words. Often, these words are adjectives describing a noun, such as in the following examples:
- wild-type plants
- C-to-A mutation
- yeast two-hybrid assay
- five-day-old plants
En dash: Wider than a hyphen, but narrower than an em dash, this type of dash has two main uses in scientific writing.
First, it indicates a range: …50–80% of the mutants...10–12 days…
Second, it indicates a connection between related words: …species–habitat associations...plant–microbe interactions…receptor–ligand pairs.
Em dash: This dash is generally used in informal writing to replace commas or parentheses that set off a phrase, so if you were writing a blog post, you might write “It may seem a little picky––okay, really picky––but trust us…” (see below). Given that most scientific writing is more formal than blog posts, we recommend not getting carried away with the em dash. Similarly, we generally spell out contractions for formal scientific writing and avoid! exclamation! marks! That said, if you want a more breezy tone, feel free to slip in a few of these friendly dashes––and, if you would like a little help writing friendly, engaging text for any audience, our writers at Peridot Scientific Communications can help!
Minus sign: This isn’t really a mark of punctuation, but authors do run into trouble with this mathematical symbol. When you’re writing, it’s often fine to use a hyphen instead of a minus sign, as many journals have copyeditors who will fix these. However, when you are making figures, the little dash can look kind of puny next to its corresponding +. In fact, some of you who have published with one of our favorite plant cell journals may have been asked by the editors to use an authentic minus sign instead of a hyphen (yes, even when superscripted on the y-axis label!). It may seem a little picky––okay, really picky––but trust us, it makes your figures look polished to have authentic minus signs.
Dash trivia: En dash is as wide as the typeset letter N and em dash is as wide as the typeset letter M.
We hope this little essay on punctuation helps clarify where you would use these little lines––and if not, feel free to let us help. All you need to do is click on the “Get Started” button to the right of this post!