|In Unicode||U+002D - HYPHEN-MINUS|
|Different from||U+2010 ‐ HYPHEN |
U+2011 ‑ NON-BREAKING HYPHEN
The hyphen-minus - is the most commonly used type of hyphen, widely used in digital documents. It is the only character that resembles a minus sign or a dash in many character sets such as ASCII or on most keyboards, so it is also used as such.[a] The name "hyphen-minus" derives from the original ASCII standard, where it was called "hyphen (minus)". The character is referred to as a "hyphen", a "minus sign", or a "dash" according to the context where it is being used.
|hyphen-minus, plus, and minus signs|
in proportional and monospaced fonts
In early monospaced font 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 a number of different dashes, an unambiguous minus sign ("Unicode minus") at code point U+2212, and various types of hyphen including the unambiguous "Unicode hyphen" at U+2010 and the hyphen-minus at U+002D. 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 recognised by many data formats and computer languages. Though the Unicode Standard states that the U+2010 hyphen is "preferred" over the hyphen-minus, the standard itself uses the hyphen-minus as its hyphen character.
In most modern fonts, the hyphen-minus is identical or very similar to the "Unicode hyphen".
In mathematical texts that include the plus sign, use of the hyphen-minus as a minus sign typically results in an unattractive appearance. Unlike the Unicode minus sign, the hyphen-minus is generally smaller and at a different height than the horizontal line in the plus sign; see the image above.[b]
Further, many word processors will word wrap at a hyphen-minus, but not after the "Unicode hyphen" sign.
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 —, and to put spaces around it - to represent a spaced en dash – . 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.
Most programming languages use the hyphen-minus for denoting subtraction and negation. It is almost never used to indicate a range, due to ambiguity with subtraction. Generally other characters, such as the Unicode U+2212 − MINUS SIGN are not recognized.
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.
The hyphen-minus character is often used when specifying command-line options, a convention popularized by Unix. Examples of the "short" form are
-q. A user can specify both by using
-Rq. Some implementations allow two hyphen-minuses to specify "long" option names as
--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.
The glyph has a code point in Unicode as U+002D - HYPHEN-MINUS; it is also in ASCII with the same value.
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'.
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) ...
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.