-
Hyphen-minus
In UnicodeU+002D - HYPHEN-MINUS
Graphical variants
﹣
U+FE63 ﹣ SMALL HYPHEN-MINUS
－
U+FF0D － FULLWIDTH HYPHEN-MINUS
Different from
Different fromU+2010 ‐ HYPHEN

U+2011 ‑ NON-BREAKING HYPHEN
U+2212 − MINUS SIGN
U+2013 – EN DASH

U+2014 — EM DASH

The hyphen-minus symbol - is the form of hyphen most commonly used in digital documents. On most keyboards, it is the only character that resembles a minus sign or a dash so it is also used for these.[1] The name hyphen-minus derives from the original ASCII standard,[2] where it was called hyphen–(minus).[3] The character is referred to as a hyphen, a minus sign, or a dash according to the context where it is being used.

Description

-+−
-+−
hyphen-minus, plus, and minus signs
in proportional and monospaced fonts

In early typewriters and character encodings, a single key/code was almost always used for hyphen, minus, various dashes, and strikethrough, since they all have a roughly similar appearance. The current Unicode Standard specifies distinct characters for several different dashes, an unambiguous minus sign (sometimes called the Unicode minus) at code point U+2212, an unambiguous hyphen (sometimes called the Unicode hyphen) at U+2010, the hyphen-minus at U+002D and a variety of other hyphen symbols for various uses. When a hyphen is called for, the hyphen-minus is a common choice as it is well known, easy to enter on keyboards, and still the only form recognized by many data formats and computer languages. Though the Unicode Standard states that the U+2010 hyphen is "preferred" over the hyphen-minus,[4] the standard itself uses the hyphen-minus as its hyphen character.[5]

In most modern computer fonts, the hyphen-minus is either identical or very similar to the Unicode hyphen.[6][a]

In mathematical texts that include the plus sign, the Unicode minus is preferred to the hyphen-minus, because its metrics match the plus sign in level and length.[b]

Uses

Typing

See also: Two consecutive hyphens and Three consecutive hyphens

This character is typed when a hyphen or a minus sign is wanted. Based on old typewriter conventions, it is common to use a pair -- to represent an em dash —,[7] and to put spaces around it  -  to represent a spaced en dash  – ; this practice is deprecated in professional typography.[8] Some word processors automatically convert these to the correct dash. The character can also be typed multiple times to simulate a horizontal line (though in most cases, repeated entry of the underscore will produce a solid line). Alternating the hyphen-minus with spaces produces a "dashed" line, often to indicate where paper is to be cut. On a typewriter, over-striking a section of text with this is used for strikethrough.

Programming languages

Most programming languages use the hyphen-minus for denoting subtraction and negation.[further explanation needed][9][10] It is rarely used to indicate a range, due to ambiguity with subtraction. Generally, other characters, such as the Unicode U+2212 − MINUS SIGN are not recognized as an operator.[citation needed]

In some programming languages (for example MySQL) -- (two hyphen-minus) mark the beginning of a comment. It can be used to start the signature block in Usenet news system. YAML uses --- (three hyphen-minuses) to end a section.

Command line

The hyphen-minus character is often used when specifying command-line options, a convention popularized by Unix. Examples of the "short" form are -R or -q. A user can specify both by using -Rq. Some implementations allow two hyphen-minuses to specify "long" option names as --recursive or --quiet. These are easier to understand when reading commands (some software does not care about the number of hyphen-minuses, and either does not allow combinations of single-letter options, or requires the user to rearrange them, so they do not match a long option). A double hyphen-minus by itself (followed by a space) indicates that there are no more options, which is useful when one needs to specify a filename that starts with a hyphen-minus. An option of just a hyphen-minus (followed by a space) may be recognized in lieu of a filename and indicates that stdin is to be read.

diff output

- is used to denote deleted lines in diff output in the context format or the unified format.

Encoding

The glyph has a code point in Unicode as U+002D - HYPHEN-MINUS. It is also in ASCII with the same value.

See also

Explanatory notes

  1. ^ In Lucida Sans Unicode, the hyphen-minus is drawn identically to the en dash.
  2. ^ The precise relationships depend on typeface design choices.

References

  1. ^ Korpela, Jukka K. (2006). Unicode explained. O'Reilly. p. 382. ISBN 978-0-596-10121-3.[dead link]
  2. ^ "3.1 General scripts" (PDF). Unicode Version 1.0 · Character Blocks. p. 30. Archived (PDF) from the original on 21 November 2021. Retrieved 10 December 2021. Loose vs. Precise Semantics. Some ASCII characters have multiple uses, either through ambiguity in the original standards or through accumulated reinterpretations of a limited codeset. For example, 27 hex is defined in ANSI X3.4 as apostrophe (closing single quotation mark; acute accent), and 2D hex as hyphen minus. In general, the Unicode standard provides the same interpretation for the equivalent code values, without adding to or subtracting from their semantics. The Unicode standard supplies unambiguous codes elsewhere for the most useful particular interpretations of these ASCII values; the corresponding unambiguous characters are cross-referenced in the character names list for this block. In a few cases, the Unicode standard indicates the generic interpretation of an ASCII code in the name of the corresponding Unicode character, for example U+0027 is APOSTROPHE-QUOTE'.
  3. ^ "American National Standard X3.4-1977: American Standard Code for Information Interchange" (PDF). National Institute of Standards and Technology. p. 10 (4.2 Graphic characters). Archived (PDF) from the original on 9 October 2022. Retrieved 10 December 2021.
  4. ^ "The Unicode Standard, Version 13.0, Chapter 6.2" (PDF). 2020. General Punctuation § Dashes and Hyphens. Archived (PDF) from the original on 22 January 2021. Retrieved 30 December 2020.
  5. ^ Korpela, Jukka. "Dashes and Hyphens § Typographic Usage". Archived from the original on 26 January 2021. Retrieved 30 December 2020.
  6. ^ Marian, Jakub. "Hyphen, minus, en-dash, and em-dash: difference and usage in English". Archived from the original on 25 December 2020. Retrieved 23 December 2020. A hyphen is usually very short (it has its own Unicode character, but you can use the hyphen-minus instead because it looks the same) ...
  7. ^ French, Nigel (2006). InDesign Type: Professional Typography with Adobe InDesign CS2. Adobe Press. p. 72. ISBN 9780321385444. Retrieved 4 July 2020.
  8. ^ Bringhurst, Robert (2004). The elements of typographic style (third ed.). Hartley & Marks, Publishers. p. 80. ISBN 978-0-88179-206-5. Retrieved 10 November 2020. In typescript, a double hyphen (--) is often used for a long dash. Double hyphens in a typeset document are a sure sign that the type was set by a typist, not a typographer. A typographer will use an em dash, three-quarter em, or en dash, depending on context or personal style. The em dash is the nineteenth-century standard, still prescribed in many editorial style books, but the em dash is too long for use with the best text faces. Like the oversized space between sentences, it belongs to the padded and corseted aesthetic of Victorian typography.
  9. ^ Ritchie, Dennis (c. 1975). "C Reference Manual" (PDF). Bell Labs. Archived (PDF) from the original on 3 April 2017. Retrieved 7 December 2016.
  10. ^ Marlow, Simon (ed.). Haskell 2010 Language Report (PDF). Archived (PDF) from the original on 4 December 2016. Retrieved 7 December 2016.[page needed]

External links

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