The hyphen-minus is the most commonly used type of
hyphen, widely used in digital
documents. It is the only character that looks like a
minus sign or a
dash
The dash is a punctuation mark consisting of a long horizontal line. It is similar in appearance to the hyphen but is longer and sometimes higher from the baseline. The most common versions are the endash , generally longer than the hyphen b ...
in many character sets such as
ASCII or on most keyboards, so it is also used as such. 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.
Description
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
dash
The dash is a punctuation mark consisting of a long horizontal line. It is similar in appearance to the hyphen but is longer and sometimes higher from the baseline. The most common versions are the endash , generally longer than the hyphen b ...
es, 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.
Further, many word processors will
word wrap at a hyphen-minus, but not after the "Unicode hyphen" sign.
Uses
Typing
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
The dash is a punctuation mark consisting of a long horizontal line. It is similar in appearance to the hyphen but is longer and sometimes higher from the baseline. The most common versions are the endash , generally longer than the hyphen b ...
,
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
Strikethrough is a typographical presentation of words with a horizontal line through their center, resulting in . Contrary to censored or sanitized (redacted) texts, the words remain readable. This presentation signifies one of two meanings. In ...
.
Programming languages
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 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
A signature block (often abbreviated as signature, sig block, sig file, .sig, dot sig, siggy, or just sig) is a personalized block of text automatically appended at the bottom of an email message, Usenet article, or forum post.
Email and Usenet
...
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 option
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
s, a convention popularized by
Unix. Examples of the "short" form are
-R or . A user can specify both by using
-Rq. Some implementations allow two hyphen-minuses to specify "long" option names as or . 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
Many words in the English vocabulary are of French origin, most coming from the Anglo-Norman spoken by the upper classes in England for several hundred years after the Norman Conquest, before the language settled into what became Modern Engli ...
of a filename and indicates that
stdin is to be read.
Encoding
The glyph has a
code point in
Unicode as ; it is also in
ASCII with the same value.
See also
*
-- (disambiguation)
--, a string of two hyphen-minus characters or - -, may approximate or refer to:
* En dash (–)
* Em dash (—), as a typewriter approximation
* Sig dashes (--), the email and Usenet signature delimiter
* For Unix commands, used as a prefix fo ...
*
Box-drawing characters including (U+2500), useful for drawing horizontal lines
*
Hyphen
*
Soft hyphen
Explanatory notes
References
External links
*
{{DEFAULTSORT:Hyphen-Minus
Punctuation
Typographical symbols