In writing, a space ( ) is a blank area that separates words, sentences, syllables (in syllabification) and other written or printed glyphs (characters). Conventions for spacing vary among languages, and in some languages the spacing rules are complex.
Typesetting uses spaces of varying length for specific purposes. The typewriter, on the other hand, can accommodate only a limited number of keys. Most typewriters have only one width of space, obtained by pressing the space bar. Following widespread acceptance of the typewriter, some spacing and other typewriter conventions, which were based on the typewriter's mechanical limitations, have influenced professional typography and other designers of printed works.
Computer representation of text eliminates all mechanical and physical limitations in any sufficiently advanced character encoding environment (such as Unicode), where spaces of various widths, styles, or language characteristics (different space characters) are indicated with unique code points. Whitespace characters include spaces of various widths, including all those that professional typesetters employ.
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 600–800 AD. Ancient Hebrew and Arabic, while they did not use spacing, used word dividers partly to compensate in clarity for the lack of vowels. The earliest Greek script also used interpuncts to divide words rather than spacing, although this practice was soon displaced by the scriptura continua. The earliest signs of spacing between words appear in Latin, where it was used extremely rarely in some manuscripts and then altogether forgotten.
Word spacing was later used by Irish and Anglo-Saxon scribes. The creation of the Carolingian minuscule by Alcuin of York, where it originated and then spread to the rest of world, including modern Arabic and Hebrew. Indeed, the actions of these Irish and Anglo-Saxon scribes marked the dramatic shift for reading between antiquity and the modern period. Spacing would become standard in Renaissance Italy and France, and then Byzantium by the end of the 16th century; then entering into the Slavic languages in Cyrillic in the 17th century, and only in modern times entering modern Sanskrit.
CJK languages don't use spaces when dealing with text containing mostly Chinese characters and kana. In Japanese, spaces may occasionally be used to separate people's family names from given names, to denote omitted particles (especially the topic particle wa), and for certain literary or artistic effects. Modern Korean however, has spaces as an essential part to its writing system (because of Western influence), given the phonetic nature of the hangul script that requires word dividers to avoid ambiguity, as opposed to Chinese characters which are mostly very distinguishable from each other. In Korean, spaces are used to separate chunks of nouns, nouns and particles, adjectives, and verbs; for certain compounds or phrases, spaces may be used or not, for example the phrase for "Republic of Korea" is usually spelled without spaces as 대한민국 rather than with a space as 대한 민국.
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.
Languages with a Latin-derived alphabet have used various methods of sentence spacing since the advent of movable type in the 15th century.
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. Psychological studies suggest "readers benefit from having two spaces after periods."
The International System of Units (SI) prescribes inserting a space between a number and a unit of measurement (being regarded as a multiplication sign) but never between a prefix and a base unit; a space (or a multiplication dot) should also be used between units in compound units.
Sometimes a narrow non-breaking space or non-breaking space, respectively, is recommended (as in, for example, IEEE Standards and IEC standards) to avoid the separation of units and values or parts of compounds units, due to automatic line wrap and word wrap.
Note: The above representation of a regular space is replaced with a non-breaking space for visibility.