Definitions

space mark

Space (punctuation)

In writing, a space () is a blank area that is devoid of content, which separates words, letters, numbers, and punctuation. Conventions for interword and intersentence spaces vary among languages, and in some cases the spacing rules are quite complex.

The Latin alphabet, used for English, was originally written scripta continua, without any word separators. Later interpuncts, centred dots, were added to make reading easier, and replaced with spaces after 600–800 AD. In typesetting, spaces have historically been of multiple lengths with particular space-lengths being used for specific typographic purposes, such as separating words or separating sentences or separating punctuation from words. Following the invention of the typewriter and the subsequent overlap of designer style-preferences and computer-technology limitations, much of this reader-centric variation has been lost in normal use.

In computer representation of text, spaces of various sizes, styles, or language characteristics (different space characters) are indicated with unique code points.

Use of the space in natural languages

Spaces between words

Modern English uses a space to separate words, but not all languages follow this practice. Spaces were not used to separate words in Latin until roughly AD 600–AD 800. Ancient Hebrew and Arabic did use spaces, partly to compensate in clarity for the lack of vowels. Traditionally, all CJK languages have no spaces: modern Chinese and Japanese (except when written with little or no kanji) still do not, but modern Korean uses spaces.

Spaces between sentences

For current practice, see here.

There are three main conventions relating to the number of spaces used to separate sentences within the same paragraph:

Double spacing can also refer to a style of line spacing: the insertion of a full additional empty line between lines of text. This is commonly used for text which may incorporate later markup or modifications, such as proof-readers' copies, legal documents, or academic assignments for correction.

Space characters and digital typography

The variable-width general-purpose space

In computer character encodings, there is a normal general-purpose space (Unicode character ; 32 decimal) whose width will vary according to the design of the typeface. Typical values range from 1/5-em to 1/3-em (in digital typography an em is equal to the nominal size of the font, so for a 10-point font the space will probably be between 2 and 3.3 points). Sophisticated fonts may have differently sized spaces for bold, italic, and small-caps faces, and often compositors will manually adjust the width of the space depending on the size and prominence of the text.

In addition to this general-purpose space, it is possible to encode a space of a specific width. See the table below for a complete list.

(In monospaced proofreading copy, only em- and en-spaces are represented using this character (which is called an em-quad or an en-quad), while other types of spaces are represented with a number sign.

Breaking and non-breaking spaces

When rendered, the generic Unicode space is often considered insignificant when appearing at the end of a line of text, or when part of a sequence of whitespace characters, so it may be omitted or "collapsed" in such circumstances. The non-breaking space, (160 decimal), renders the same as a normal space but is expressly non-collapsible. It is often used to prevent line wrapping or to indent text, though best World Wide Web practice prescribes using CSS for the latter purpose.

Hair spaces around dashes

Typically, both en dashes and em dashes are set continuous with the text (as illustrated by use in the Chicago Manual of Style, 6.80, 6.83–86). However, an em dash can optionally be surrounded with a so-called hair space, (8202 decimal). This space should be much thinner than a normal space, and is seldom used on its own. It can be written in HTML by using the numeric character reference   or  . Very few user agents are able to render a hair space correctly: in most cases the result is an unwanted symbol or a question mark on the screen, depending on the font and renderer capabilities.

Normal space versus hair space
Normal space left right
Normal space with em dash left — right
Hair space with em dash left — right
No space with em dash left—right

Table of spaces

Unicode defines several space characters with specific semantics and rendering characteristics, as shown in the table below. Depending on the browser and fonts used to view this table, not all spaces may display properly:

Space characters defined in Unicode
Code No break HTML entity Name In Block Display Description
U+0020   Space Basic Latin ] [ Normal space, same as ASCII character 0x20
U+00A0   No-Break Space Latin-1 Supplement ] [ Identical to U+0020, but not a point at which a line may be broken
U+1680   Ogham Space Mark Ogham ] [ Used for interword separation in Ogham text. Normally a vertical line in vertical text or a horizontal line in horizontal text, but may also be a blank space in "stemless" fonts. Requires an Ogham font.
U+180E ᠎ Mongolian Vowel Separator,
or MVS
Mongolian ]᠎[ A thin space character used in Mongolian to cause the final two characters of a word to take on different shapes.
U+2002   En Space,
or Nut
General Punctuation ] [ Width of one en (half of one em). U+2000 En Quad is canonically equivalent to this character (En Space is preferred).
U+2003   Em Space,
or Mutton
General Punctuation ] [ Width of one em. U+2001 Em Quad is canonically equivalent to this character (Em Space is preferred).
U+2004   Three-Per-Em Space,
or Thick Space
General Punctuation ] [ One third of an em wide
U+2005   Four-Per-Em Space,
or Mid Space
General Punctuation ] [ One fourth of an em wide
U+2006   Six-Per-Em Space General Punctuation ] [ One sixth of an em wide. In computer typography sometimes equated to U+2009.
U+2007   Figure Space General Punctuation ] [ In fonts with monospaced digits, equal to the width of one digit
U+2008   Punctuation Space General Punctuation ] [ As wide as the narrow punctuation in a font
U+2009   Thin Space General Punctuation ] [ One fifth (sometimes one sixth) of an em wide
U+200A   Hair Space General Punctuation ] [ Thinner than a thin space
U+200B ​ Zero Width Space,
or ZWSP
General Punctuation ]​[ Used to indicate word boundaries to text processing systems when using scripts that do not use explicit spacing; normally not a visible separation, but it may expand in passages that are fully justified. In HTML pages this space can be used as a potential line-break in long words as a replacement for the non-standard tag. However, it is not supported in all web browsers, most notably Internet Explorer version 6 and below).
U+200C ‌ Zero Width Non Joiner,
or ZWNJ
General Punctuation ]‌[ When placed between two characters that would otherwise be connected, a ZWNJ causes them to be printed in their final and initial forms, respectively.
U+200D ‍ Zero Width Joiner,
or ZWJ
General Punctuation ]‍[ When placed between two characters that would otherwise not be connected, a ZWJ causes them to be printed in their connected forms.
U+202F   Narrow No-Break Space General Punctuation ] [ Similar to U+00A0 No-Break Space
U+205F   Medium Mathematical Space General Punctuation ] [ Used in mathematical formulae
U+2060 ⁠ Word Joiner General Punctuation ]⁠[ Identical to U+200B, but not a point at which a line may be broken. Introduced in Unicode 3.2 to replace the deprecated "zero width no-break space" function of the U+FEFF character.
U+3000   Ideographic Space CJK Symbols and Punctuation ] [ As wide as a CJK character cell (fullwidth)
U+FEFF  Zero Width No-Break Space
= Byte Order Mark (BOM)
Arabic Presentation Forms-B ][ Used primarily as a Byte Order Mark character. Use as an indication of non-breaking is deprecated as of Unicode 3.2. See U+2060 instead.

Unicode also provides some visible characters to stand in for space when necessary in the "Control Pictures" block: the Symbol For Space ␠ (U+2420), the Blank Symbol ␢ (U+2422), and the Open Box ␣ (U+2423). The interpunct · is also often used to represent a space in word processing programs such as Microsoft Word.

Use of the space in computing

In programming language syntax, spaces are frequently used to explicitly separate tokens. Aside from this use, spaces and other whitespace characters are usually ignored by modern programming languages. Exceptions are Haskell, ABC, and Python, which use the amount of whitespace in indentation to indicate the bounds of a block, and a whimsical language called Whitespace, where whitespace is the only meaningful syntactical element.

Text editors, word processors, and desktop publishing software differ in how they represent whitespace on the screen, and how they represent spaces at the ends of lines longer than the screen or column width. In some cases, spaces are shown simply as blank space; in other cases they may be represented by an interpunct or other symbols. Many different characters (described below) could be used to produce spaces, and non-character functions (such as margins and tab settings) can also affect whitespace.

Space characters in markup languages

Generalised markup languages, such as SGML, do not treat space characters differently from other characters.

However, special-purpose markup languages may do. In particular, web markup languages such as XML and HTML treat whitespace characters specially, including space characters, for programmers' convenience. One or more space characters read by conforming Display-time processors of those markup languages are collapsed to 0 or 1 space, depending on their semantic context. For example, double (or more) spaces within text are collapsed to a single space, and spaces which appear on either side of the "=" that separates an attribute name from its value have no effect on the interpretation of the document. Element end tags can contain trailing spaces, and empty-element tags in XML can contain spaces before the "/>".

In XML attribute values, sequences of whitespace characters are treated as a single space when the document is read by a parser. Whitespace in XML element content is not changed in this way by the parser, but an application receiving information from the parser may choose to apply similar rules to element content. An XML document author can use the xml:space="preserve" attribute on an element to force the parser to discourage the downstream application from altering whitespace in that element's content.

In most HTML elements, a sequence of whitespace characters is treated as a single inter-word separator, which may manifest as a single space character when rendering text in a language that normally inserts such space between words. Conforming HTML renderers are required to apply a more literal treatment of whitespace within a few prescribed elements, such as the pre tag and any element for which CSS has been used to apply pre-like whitespace processing. In such elements, space characters will not be "collapsed" into inter-word separators.

In both XML and HTML, the non-breaking space character, along with other non-"standard" spaces, is not treated as collapsible "whitespace", so it is not subject to the rules above.

See also

References

External links

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