How to Use Em Dashes (–), En Dashes (–), and Hyphens (-)

Here's an easy, if not always precise way to remember:

* Hyphens connect things, such as compound words: double-decker, cut-and-dried, 212-555-5555.

* EN dashes make a range between things: Boston–San Francisco flight, 10–20 years: both connect not only the endpoints, but define that all the space between is included. (Compare the last usage with the phone number example under Hyphens.)

* EM dashes break things, such as sentences or thoughts: 'What the—!'; A paragraph should express one idea—but rules are made to be broken.

Unicode has the original ASCII hyphen-minus (U+002d), as well as a dedicated hyphen (U+2010), other functional hyphens such as soft and non-breaking hyphens, and a dedicated minus sign (U+2212), and some variations of minus such as subscript, superscript, etc.

There's also the figure dash "‒" (U+2012), essentally a hyphen-minus that's the same width as numbers and used aesthetically for typsetting, afaik. And don't overlook two-em-dashes "⸺" and three-em-dashes "⸻" and horizontal bars "―", the latter used like quotation marks!

I prefer the dedicated minus (U+2212) over the hyphen-minus (U+002d) for mathematical use because they look different in most font faces.

Are there cases where the dedicated hyphen (U+2010) is preferred over the hyphen-minus?

G. Brandon Robinson swears by U+2010 for hyphens in groff's Unicode output [0], but I see it as a hypercorrection. The most common convention by far (among authors who use Unicode and care about dashes) is to use U+002D for hyphens and U+2212 for minus signs. Not even the Unicode Consortium uses U+2010 for hyphens in its documents, and I'm not aware of any major organization that does.

As far as appearance goes, almost all fonts I've looked at make U+2010 identical to U+002D (i.e., they don't put any 'minus' into the 'hyphen-minus'), but a few make U+2010 a smidgeon shorter.

[0] https://news.ycombinator.com/item?id=38121765