The use of a single character for both hyphen and minus was a compromise made in the early days of fixed-width typewriters and computer displays. However, in proper typesetting and graphic design, there are distinct characters for hyphens, dashes, and the minus sign. Usage of the hyphen-minus nonetheless persists in many contexts, as it is well-known, easy to enter on keyboards, and in the same location in all common character sets.
As the minus sign
The minus sign is nominally the same width as the plus sign. In proportional typefaces it is longer than a hyphen. During typesetting a word wrap may also occur following a hyphen-minus, unlike the minus sign proper which is treated as a mathematical symbol. These differences make "-" as a substitute for minus signs undesirable in professional typography.
On typewriters, it was conventional to use a pair of hyphens to represent an em dash, and this convention is still sometimes used in computer text.
The hyphen-minus is often used to represent an en dash, which may be used to indicate ranges (such as a time range of "2000–2004"), direction (as in "The Los Angeles–London flight"), and other cases of connection. The en dash is normally longer (the width of a letter "n") than a hyphen, though in a fixed-pitch or typewriter font there is no difference. The hyphen connects closely, the en dash less closely, while the em dash (the width of a letter "m") separates.
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- "Hyphens, En Dashes, Em Dashes". The Chicago Manual of Style Online. Retrieved 25 January 2017.