Appropriate symbol for typesetting negative numbers

dstringham's picture


Looking to settle a discussion over which is the appropriate symbol to denote a negative number: a hyphen or an en dash. Haven't been able to find any definitive rules or historical samples of this. Opinions and/or facts are appreciated.

oldnick's picture

In ye olden days, an en dash was preferred because numbers were generally one en wide; the consistency in width made columnar setting easier.

Stickley's picture

It's also common to use a minus sign. Being a math figure and having dedicated symbol, I'd say that's a good way to go too.

cuttlefish's picture

Many fonts don't have the U+2212 minus sign, but any that is intended for typesetting math really ought to. If it's just an incidental negative number in a body of text, and not a mathematics publication, a U+002D hyphen-minus should be adequate.

Just my opinion.
I'd go with oldnick and use an en-dash in columnar setting, just not in body text.

Nick Shinn's picture

I often (eg Bodoni Egyptian, Figgins) make the en-dash and minus identical, so that the en-dash will "do" for the minus sign, and matches the plus sign in alignment, weight, and width.

But design-wise that's not always in the best interests of the typeface, so I don't make it a standard practice.

cerulean's picture

The font you're using will probably have a plus sign and an equal sign. The minus is supposed to match them in length. If the font lacks a minus, use the nearest thing to it, which will usually be the en dash. If it's noticeably different from the ideal length, you can scale it!

The substitution of a hyphen only started to happen with monospaced typewriters and computers. Bringing that habit back to a proportional face is bad practice. In most text faces a hyphen is rather too small and can get overlooked. No matter what the context, the difference between a negative number and a positive one is going to be important enough that it should break the color of a body of text.

dtw's picture

Quite often our (academic journal) authors will use a hyphen for negative numbers in their manuscripts (simply because it's a helluva lot easier to get at than the proper minus, and/or they're unaware that the font may contain such a separate character), but our copyeditors will always replace it with a minus for the final typeset articles.

quadibloc's picture

The substitution of a hyphen only started to happen with monospaced typewriters and computers. Bringing that habit back to a proportional face is bad practice.

simply because it's a helluva lot easier to get at than the proper minus, and/or they're unaware that the font may contain such a separate character

This is one symptom of a larger problem.

In Latin-alphabet languages other than English, things are made worse by the need to accommodate accented letters on the conventional keyboard. But even on the English-language keyboard, several character positions make sense for computer programming only. They don't even make sense for "word processing"... business document typing, which used to be monospaced, but which, even with a proportional typestyle, is not typesetting.

An English-language keyboard, thus, for use in the U.S. environment, ought to be switchable into a "word processing" mode, where the following characters get substituted on the keys:

~ is replaced by ±
` is replaced by º
< is replaced by ¶
> is replaced by §
| is replaced by ¼
\ is replaced by ½
{ is replaced by £
} is replaced by ¾
^ is replaced by ¢

For typesetting mode, it is necessary to replace the underscore with the em-dash, to make † and ‡ accessible, and, ideally, ⅛, ⅜, ⅝, and ⅞ as well. (One doesn't need @ and # in that mode, which will help a little - ~ and ` can also have their substitutes changed. That's still two characters short, but the European keyboard does have one extra key...)

And, as I've noted, for typesetting, the keyboard really should provide small capitals as a third shift, which would require turning Unicode upside down, as small capitals are not currently recognized as a "case".

If one is going to use a special symbol for minus, however, one has (in however much of a small way) entered into the domain of the typesetting of mathematics. At this point, one has reached a level at which "Abandon all hope, ye who enter here" or at least "May God have mercy on your soul" seems like the appropriate comment.

Thus, while it is already foolish to hope that Windows (or even the Mac, which at least does offer special characters with an alt shift on its default keyboard) might someday offer "US English - Word Processing" and "US English - Typesetting" alternate keyboard layouts... making the math stuff handy goes beyond that.

Not that it's impossible; after all, keyboards that looked like this

(this is a drawing I made for my web page, so as to avoid rights questions; there are photographs of this keyboard on the web as well, if you would like to see the real thing) existed, and there are the three keyboard layouts for the IBM Selectric Composer for Mathematical Greek, Mathematical and Technical elements, and various mathematical keyboard layouts for photocomposition machines... but we don't even get the APL layout offered to us as standard.

Igor Freiberger's picture

Why not to create a keyboard with access to additional glyphs through AltGr (the right Alt key)? It's quite simple with MS Keyboard Editor, a free tool from Microsoft.

Mine is a standard US international keyboard expanded with AltGr and Shift+AltGr. Some combination do not work if already set, as with InDesign shortcuts. But this is the only issue. My setup:

[AltGr] ¹²³¤€¼½¾‘’–× äåé®þüúíóöªº§ áðêøãõ 朩•ñµç¡¿
[Sh+AltGr] £¢⅓⅔₢«»±÷ ÄÅÉÞÜÚÍÓÖ°¦ Á¶ÐÊØÃÕ ÆŒÑÇ

I suppose something similar is possible in MacOS.

quadibloc's picture

I downloaded MS Keyboard Editor, but I had trouble getting it to work even on the system I have with Vista installed, never mind on the computer with XP that I use most often.

I am, though, happy that a new keyboard design, an international standard, without the issues of the US International keyboard (the dead-key behavior of ' and " and other keys) will be available at least in newer versions of Windows.

Igor Freiberger's picture

MSKE works perfectly in XP. With my 64-bit Vista, I had to restore a clean system image to use it. There is some conflict with a further installed program, but I cannot identify which one (life is a lot easier using system images and restoring them every time something goes wrong).

Of course, improved input systems as you refered are welcome. A perfect keyboard would have dynamic light-identified keys, which change with target use, as one already can do with some UI. An idea to 2021, maybe.

quadibloc's picture

Well, it is true that a gentleman in Russia is already marketing the Optimus Maximus keyboard - and a less expensive version, the Optimus Popularis, is also under development.

I'm not sure that such a device, appealing though it is, is actually the answer. Integration with the operating system is more important, for example.

Here is an illustration of how a U.S. keyboard could integrate the ordinary word processing and typesetting layouts, if it took the ANSI layout further, in order to more strictly follow the old typewriter style of layout:

Joshua Langman's picture

The current Mac keyboard alternates:

Plain: `1234567890-= qwertyuiop[]\ asdfghjkl;' zxcvbnm,./
Shift: ~!@#$%^&*()_+ QWERTYUIOP{}| ASDFGHJKL:" ZXCVBNM<>?
Option: `¡™£¢∞§¶•ªº–≠ œ∑´®†¥¨ˆøπ“‘«   åß∂ƒ©˙∆˚¬…æ   Ω≈ç√∫˜µ≤≥÷
Opt/shift: `⁄€‹›fifl‡°·‚—±   Œ„´‰ˇÁ¨ˆØ∏”’»   ÅÍÎÏ˝ÓÔÒÚÆ   ¸˛Ç◊ı˜Â¯˘¿

It is possible, with the option key, to type most common special characters for the Latin alphabet (other than special typesetter's spaces) if you know the keystrokes involved. En dash, for instance, is opt+hyphen. Accents work as follows:

á = opt+e; then a

Some other commonly used typographic symbols — I have these memorized from frequent use:

em dash — opt+shift+hyphen
ellipsis … opt+semicolon
midpoint · opt+shift+9
bullet • opt+8
Spanish question ¿ opt+shift+question
Spanish exclamation ¡ opt+1
aesc æ opt+comma
oethel œ opt+q

There are a few other InDesign-specific ones, like cmd+n for an en space and cmd+m for an em space.

Bringhurst, by the way, proposes a method of combining opt/shift keys to cover all characters needed for (I believe) all uses of the Latin alphabet in European languages, plus a few additional characters.

Oh, and to address the original topic of this thread, I use an en dash for minus, with spaces on either side if in an equation, without spaces if for a single negative number.

3 – 2 = 1

–30 ˚F

Nick Shinn's picture

I have always used those Mac keyboard codes.
If you were going to do proper typography in the early days of digital you had to know them, because there were no glyph palettes.
And option-shift-leftbracket etc. for curly quotes, because there was no layout feature to do it automatically.

cerulean's picture

I'm looking at my Microsoft keyboard, and I notice that the minus key on the keypad is printed with a proper minus sign, distinguishable from the hyphen on the hyphen key on the top row. But all it does is input a hyphen, of course. Seems like if you're going to have a whole area of completely redundant keys just for calculating, well...

dtw's picture

Indeed - before all those alternate-keyboard options (which are fine, but you've got to be the sort of author who CARES to start using any of them), it would be nice if the minus key on the numeric keypad would simply, by default, insert U+2212 instead of U+002D!

quadibloc's picture

it would be nice if the minus key on the numeric keypad would simply, by default, insert U+2212 instead of U+002D!

That might make sense under some conditions - under which the * and / keys on the numeric keypad ought to insert U+00D7 (×) and U+00F7 (÷) respectively too. The trouble, of course, is determining when those conditions apply.

Under normal conditions, it would be extremely confusing for the keyboard to generate anything outside of the conventional ASCII range from U+0000 to U+007F from any key which could plausibly be associated with a character within that range. Of course, defining "normal" conditions as typing text into Notepad, Programmer's File Editor, or gedit for input into, say, a FORTRAN compiler may seem to some as being perverse these days...

Oh, and I even have a cute little reference chart of the extra characters on the Macintosh:

having been aware of its useful feature in this area.

dtw's picture

Fair point. :^)

johnbutler's picture

I second MS Keyboard Layout Creator. I used it to add a bunch of Unicode stuff to my keyboard layout. (inch & foot ′ ″, math, long ſ, some ❦❧ fleurons &c.)

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