In writing, a space ( ) is a blank area devoid of content, serving to separate words, letters, numbers, and punctuation. Conventions for interword and intersentence spaces vary among languages, and in some cases the spacing rules are quite complex. In the classical period, Latin was written with interpuncts (centred dots) as word separators, but that practice was abandoned sometime around AD 200 in favour of scriptio continua, i.e., with the words running together without any word separators. In around AD 600–800, blank spaces started being inserted between words in Latin, and that practice carried over to all languages using the Latin alphabet (including English and most other Western European languages).
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 was 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. Whitespace characters include the various types of spaces, tabs, line breaks, paragraph breaks, page breaks, and related characters. These are used in digital typesetting, inputting commands, programming, and markup languages.
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 600–800. 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.
Runic texts use either an interpunct-like or a colon-like punctuation mark to separate words. There are two Unicode characters dedicated for this: U+16EB ᛫ runic single punctuation and U+16EC ᛬ runic multiple punctuation.
Spaces between sentences
Languages with a Latin-derived alphabet have used various methods of sentence spacing since the advent of movable type in the 15th century.
- One space (French Spacing). This is a common convention in most countries that use the ISO basic Latin alphabet for published and final written work, as well as digital (World Wide Web) media. Web browsers usually do not differentiate between single and multiple spaces in source code when displaying text, unless text is given a "white-space" CSS attribute. Without this being set, collapsing strings of spaces to a single space allows HTML source code to be spaced in a more readable way, at the expense of control over spacing of the rendered page.
- Double space (English Spacing). It is sometimes claimed that this convention stems from the use of the monospaced font on typewriters. However, instructions to use more spacing between sentences than words date back centuries, and two spaces on a typewriter was the closest approximation to typesetters' previous rules aimed at improving readability. Wider spacing continued to be used by both typesetters and typists until the Second World War, after which typesetters gradually transitioned to word spacing between sentences in published print, while typists continued the practice of using two spaces.
- One widened space, typically one-and-a-third to slightly less than twice as wide as a word space. This spacing was sometimes used in typesetting before the 19th century. It has also been used in other non-typewriter typesetting systems such as the Linotype machine and the TeX system. Modern computer-based digital fonts can adjust the spacing after terminal punctuation as well, creating a space slightly wider than a standard word space.
- No space. According to Lynne Truss, "young people" today using digital media "are now accustomed to following a full stop with a lower-case letter and no space".
There has been some controversy regarding the proper amount of sentence spacing in typeset material. The Elements of Typographic Style states that only a single word space is required for sentence spacing since "Larger spaces...are themselves punctuation." [clarification needed]
Spaces and unit symbols
The International System of Units, or SI, and the style guide of the English-language Wikipedia recommend a (non-breaking) space between a number and its units, as well as between units in the case of compound units, but never between a prefix and the basic unit.
- 5.0 cm not 5.0 c m
- 45 kg not 45kg or 45 k g
- 32 °C not 32°C or 32° C
- 20 kN m not 20 kNm or 20 k Nm
- 50 % not 50% (Note: % is not an SI unit, and Wikipedia does not follow this SI recommendation.)
The only exceptions to this rule in the SI are for the symbols for degree, minute, and second for plane angle, as in 30° 22′ 8″.
Some sources say that a hyphen may be inserted between a numeral and a symbol used adjectivally, for the sake of clarity:
- 35-mm film
- 60-W bulb
However, some other style guides, including Wikipedia's, deprecate hyphenation in these cases. The SI allows a hyphen between the numeral and the unit only when the name of the unit is spelled out, as 35-millimetre film.
- Einsohn, Amy (2006). "Punctuation, Eyeballing every mark". The Copyeditor's Handbook: A Guide for Book Publishing and Corporate Communications (2nd ed.). Berkeley, Los Angeles, London: University of California Press. p. 113. ISBN 9780520246881. Retrieved 2010-04-25. "If you are working on documents that will be printed without any intervention from a compositor (e.g., documents produced on the office laser printer), you will have to carefully scrutinize every piece of punctuation to be sure that the document contains the correct character (see table 5). You should also delete any extra wordspacing before and after punctuation marks. The conventions are: One space follows sentence-ending punctuation mark (period, question mark, or exclamation point). One space follows comma, colon, or semicolon ..."
- Thomas A. Fine. "How many spaces at the end of a sentence? One or two?".
- Farhad Manjoo (2011-01-13). "Space Invaders: Why you should never, ever use two spaces after a period.". Slate. Retrieved 2011-03-29.
- Heraclitus (1 November 2011). "Why two spaces after a period isn't wrong".
- Felici, James (2003). The Complete Manual of Typography: A Guide to Setting Perfect Type. Berkeley, CA: Peachpit Press. p. 80. ISBN 0321127307.;
- David Spencer (24 May 2011). "The Curious Misconception Surrounding Sentence Spacing". Type Desk. Matador. Retrieved 27 May 2011.
- Bringhurst, Robert (2004). The Elements of Typographic Style (3 ed.). Washington and Vancouver: Hartley & Marks. p. 28. ISBN 0881792063. "2.1.4 Use a single word space between sentences. In the nineteenth century, which was a dark and inflationary age in typography and type design, many compositors were encouraged to stuff extra space between sentences. Generations of twentieth century typists were then taught to do the same, by hitting the spacebar twice after every period [full stop]. Your typing as well as your typesetting will benefit from unlearning this quaint Victorian habit. As a general rule, no more than a single space is required after a period, colon, or any other mark of punctuation"
- Schriver, Karen (1997). Dynamics in Document Design: Creating Text for Readers (1 ed.). New York: Wiley. p. 502. ISBN 9780471306368. "Use one space (not two) after these punctuation marks [sc. period, question mark, exclamation point, or colon], as the practice of using two spaces is just another holdover from using a typewriter."
- Strauss, Jane (2007). "Spacing with Punctuation". The Blue Book of Grammar and Punctuation: An Easy-to-Use Guide with Clear Rules, Real-World Examples, and Reproducible Quizzes (10 ed.). Jossey-Bass. p. 176. ISBN 9780470222683. Retrieved 2010-04-25. "Rule 1. With a computer, use only one space following periods, commas, semicolons, colons, exclamation points, question marks, and quotation marks. The space needed after these punctuation marks is proportioned automatically. With some typewriters and word processors, follow ending punctuation with two spaces when using a fixed-pitch font."
- "2.49 Leading and spacing". The GPO Style Manual (30 ed.). Washington: The U.S. Government Printing Office. 2008. p. 469. ISBN 9780160818127. Retrieved 2010-04-25. "A single justified word space will be used between sentences. This applies to all types of composition."
- "FAQ: How many spaces should I leave after a period or other concluding mark of punctuation?". MLA Handbook for Writers of Research Papers (7 ed.). Modern Language Association. 2009. p. 292. ISBN 978-0-87352-297-7. Retrieved 2010-04-25. "Publications in the United States today usually have the same spacing after a punctuation mark as between words on the same line. Since word processors make available the same fonts used by typesetters for printed works, many writers, influenced by the look of typeset publications, now leave only one space after a concluding punctuation mark. In addition, most publishers' guidelines for preparing electronic manuscripts ask authors to type only the spaces that are to appear in print."
- "FAQ: How many spaces should I leave after a period or other concluding mark of punctuation?". The Chicago Manual of Style (7 ed.). University of Chicago Press. 2009. p. 292. ISBN 9780873522977. Retrieved 2010-04-25. "Publications in the United States today usually have the same spacing after a punctuation mark as between words on the same line. Since word processors make available the same fonts used by typesetters for printed works, many writers, influenced by the look of typeset publications, now leave only one space after a concluding punctuation mark. In addition, most publishers' guidelines for preparing electronic manuscripts ask authors to type only the spaces that are to appear in print."
- "The Chicago Manual of Style Online (Q&A: One Space or Two?)". University of Chicago Press. 2003. Retrieved 2010-04-25. "The view at CMOS is that there is no reason for two spaces after a period in published work. Some people, however—my colleagues included—prefer it, relegating this preference to their personal correspondence and notes. I’ve noticed in old American books printed in the few decades before and after the turn of the twentieth century (ca. 1870–1930 at least) that there seemed to be a trend in publishing to use extra space (sometimes quite a bit of it) after periods. And many people were taught to use that extra space in typing class (I was). But introducing two spaces after the period causes problems: (1) it is inefficient, requiring an extra keystroke for every sentence; (2) even if a program is set to automatically put an extra space after a period, such automation is never foolproof; (3) there is no proof that an extra space actually improves readability—as your comment suggests, it’s probably just a matter of familiarity (Who knows? perhaps it’s actually more efficient to read with less regard for sentences as individual units of thought—many centuries ago, for example in ancient Greece, there were no spaces even between words, and no punctuation); (4) two spaces are harder to control for than one in electronic documents (I find that the earmark of a document that imposes a two-space rule is a smattering of instances of both three spaces and one space after a period, and two spaces in the middle of sentences); and (5) two spaces can cause problems with line breaks in certain programs. So, in our efficient, modern world, I think there is no room for two spaces after a period. In the opinion of this particular copyeditor, this is a good thing."
- "Chapter 5. Manuscript Preparation and Sample Papers to be Submitted for Publication". Publication Manual of the American Psychological Association (aka APA Style) (5 ed.). Washington: American Psychological Association. 2001. p. 439. ISBN 9781557987907. Retrieved 2010-04-25. "5.11 Spacing and Punctuation: Space once after all punctuation as follows: after commas, colons, and semicolons; after punctuation marks at the end of sentences; after periods that separate parts of a reference citation; and after the periods of the initials in personal names (e.g., J. R. Zhang). Exception: Do not use space after internal periods in abbreviations (e.g., a.m, i.e., U.S.)"
- Style Manual: for Authors, Editors and Printers (aka AGPS Style) (6 ed.). Stafford, Australia: Wiley Australia, The Commonwealth Government of Australia Printing Office. 2002. p. 117. ISBN 978-0-7016-3647-0. Retrieved 2010-04-25. "In typewritten (as distinct from typeset) material, it was customary to place two spaces after a colon, semicolon, full stop or other sentence closing punctuation. Programs for word processing and desktop publishing offer more sophisticated, variable spacing, so this practice of double spacing is now avoided because it can create distracting gaps on a page."
- Mergenthaler Linotype Company (1940). Linotype Keyboard Operation: Methods of Study and Procedures for Setting Various Kinds of Composition on the Linotype. Mergenthaler Linotype Company. cited in Mark Simonson (5 March 2004). "Double-spacing after Periods". Typophile. Typophile. Retrieved 5 April 2010.
- Eijkhout, Victor (2008), TeX by Topic, A TeXnician's Reference (pdf), Lulu, pp. 185–188
- Felici, James (2003). The Complete Manual of Typography: A Guide to Setting Perfect Type. Berkeley, CA: Peachpit Press. p. 80. ISBN 0-321-12730-7.; Fogarty, Mignon (2008). Grammar Girl's Quick and Dirty Tips for Better Writing (Quick and Dirty Tips). New York: Holt Paperbacks. p. 85. ISBN 978-0-8050-8831-1.; Straus, Jane (2009). The Blue Book of Grammar and Punctuation: An Easy-to-Use Guide with Clear Rules, Real-World Examples, and Reproducible Quizzes (10th ed.). San Francisco, CA: Jossey-Bass. p. 52. ISBN 978-0-470-22268-3.
- Truss, Lynn (2004). Eats, Shoot & Leaves: The Zero Tolerance Approach to Punctuation. New York: Gotham Books. p. 25. ISBN 1-59240-087-6.
- Bringhurst, Robert (2004). The Elements of Typographic Style (3.0 ed.). Washington and Vancouver: Hartley & Marks. pp. 29–30. ISBN 0-88179-206-3.
- The International System of Units (SI) (8 ed.). International Bureau of Weights and Measures (BIPM). 2006. p. 133..
- "Wikipedia: Manual of Style (dates and numbers)". Section 'Units of measurement': Wikipedia. Retrieved 28 January 2011.
- Saenger, Paul (1997). Space Between Words: The Origin of Silent Reading. Stanford, Calif: Stanford University Press. ISBN 9780804726535. OCLC 35548786.