Back in the days of typewriters, all you had was the hyphen, and if you wanted something stronger, you typed two hyphens. But nowadays, with proportional fonts and all, we have the hyphen, the N-dash, and the M-dash. (Typographers, with their fonts and printing presses, always had these, by the way.)
Trouble is, lots of folks don’t know how to use all these professional tools. But I ran into an article the other day written by someone who did! The organization is Axios, the series is Axios Science, and the writer is Andrew Freedman. Link:
https://www.axios.com/newsletters/axios-science-b9b38725-e940-4c81-867d-64c7cac89f53.html
First, a hyphen, used correctly:
They used high-resolution climate models based on various emissions scenarios to project future changes in key cloud forest variables.
“high-resolution” is a compound adjective. Correct.
Next, an N-dash:
The study finds that in about 25–45 years, 70%–86% of páramo are likely to be drier or “be subject to tree invasion.”
You use the N-dash to indicate a range; in this case “25 to 45” and “70 to 86.” Correct.
Finally the M-dash, in the next article:
Considerable time is spent focusing on whether a planet is in its star’s “habitable zone” — an orbit in which liquid water can be sustained on the surface — but that alone can’t predict whether life will exist.
Use M-dashes for some kind of break, or as a strong set of parentheses to set off something important, which he did here. Technically he doesn’t need the spaces around the M-dashes (I don’t use the spaces) but it’s allowed. Maybe he wanted to strengthen the effect.
Here’s the picture that went with the first article:
