Wikipedia:Reference desk archive/Mathematics/2006 July 6

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[edit] What is the "-" Symbol called as?

We use "-" sign to get the negative of a number. i.e 20 can be made as (-)20. What do we call this - sign. I just know that this is not called as "minus sign". Could you please answer my doubt?

I call it a minus sign. So do typographers. It is very similar to a hyphen, and often the same character is used. Notinasnaid 11:58, 6 July 2006 (UTC)

It is a minus sign. That's its official name in unicode too. McKay 11:59, 6 July 2006 (UTC)

Typographically speaking, the minus sign (−) is different from the hyphen (-), and both of these are different from the en dash (–) and the em dash (—); see dash. The minus sign is usually the same width as the plus sign (+), because math looks better that way. —Bkell (talk) 14:27, 6 July 2006 (UTC)

It's also called the unary minus, to distinguish it from the binary minus (we seem to be missing an article or redirect on unary minus and binary minus, any takers?). --cesarb 17:02, 6 July 2006 (UTC)

Please, when giving examples of characters, also provide the Unicode codepoint or HTML named entity or some such. Why? Because the appearance depends on the typeface, so may communicate nothing. For example, in a font like Courier there is little or no visible difference:

-	U+002D	HYPHEN-MINUS	-
‐	U+2010	HYPHEN	‐
‒	U+2012	FIGURE DASH	‒
–	U+2013	EN DASH	–
—	U+2014	EM DASH	—
−	U+2212	MINUS SIGN	−

This possible confusion would not be obvious to a person using a font like Helvetica or Arial:

-	U+002D	HYPHEN-MINUS	-
‐	U+2010	HYPHEN	‐
‒	U+2012	FIGURE DASH	‒
–	U+2013	EN DASH	–
—	U+2014	EM DASH	—
−	U+2212	MINUS SIGN	−

And depending on the character and the font, the only visible mark might be a missing character symbol. So be kind.

Back to the topic at hand, Unicode distinguishes three characters: the hypen-minus (the old ASCII character which does double duty), the hyphen (which seems rarely used), and the minus (which we prefer in Wikipedia mathematics). --KSmrq^T 20:27, 6 July 2006 (UTC)

don't forget that some elementary/algebra textbooks (the ones we used) like to put the minus at the top of the line, like the bar in T, like T7, without the serifs or the vertical part, so that it doesn't look at all like a -. Thus 5 + T7 doesn't look like 5 + -7 at all. Again, that's not a T, just my representation, just look at the top of the T and ignore the serifs. Maybe "T minus | sans serif". Gives a whole new meaning to t minus.  :) 82.131.188.84 20:30, 6 July 2006 (UTC).

If you are speaking of the distinction between negation and subtraction, probably the notation you want is "9 + ¯4", as opposed to "9 − 4". (The APL programming language also makes such a distinction, and the character used seems to be U+00AF, MACRON, as shown here.) --KSmrq^T 23:22, 6 July 2006 (UTC)

I suppose it could be either the macron, or the overline:

¯	U+00AF	MACRON	¯
‾	U+203E	OVERLINE	‾

depending on how long you want it to be.-gadfium 03:20, 7 July 2006 (UTC)

You suppose wrong, at least insofar as APL is concerned. This is not a guessing game based on appearance; the Unicode standard defines the codepoint used for macron as equal to the APL overbar. But if you are not concerned about APL, the standard defines nothing specific for unary minus (that I know of).

Frankly, Unicode is confusing for mathematics, because it associates specific meanings with codepoints, but mathematicians do not always use symbols so consistently. --KSmrq^T 04:26, 7 July 2006 (UTC)