Sentence spacing
Sentence spacing concerns how spaces are inserted between sentences in typeset text and is a matter of typographical convention. Since the introduction of movable-type printing in Europe, various sentence spacing conventions have been used in languages with a Latin alphabet. These include a normal word space, a single enlarged space, and two full spaces.
Until the 20th century, publishing houses and printers in many countries used additional space between sentences. There were exceptions to this traditional spacing methodsome printers used spacing between sentences that was no wider than word spacing. This was French spacing, synonymous with single-space sentence spacing until the late 20th century. With the introduction of the typewriter in the late 19th century, typists used two spaces between sentences to mimic the style used by traditional typesetters. While wide sentence spacing was phased out in the printing industry in the mid-20th century, the practice continued on typewriters and later on computers. Perhaps because of this, many modern sources now incorrectly claim that wide spacing was created for the typewriter.
The desired or correct sentence spacing is often debated, but most sources now state that an additional space is not necessary or desirable. From around 1950, single sentence spacing became standard in books, magazines, and newspapers, and the majority of style guides that use a Latin-derived alphabet as a language base now prescribe or recommend the use of a single space after the concluding punctuation of a sentence. However, some sources still state that additional spacing is correct or acceptable. Some people preferred double sentence spacing because that was how they were taught to type. The few direct [|studies] conducted since 2002 have produced inconclusive results as to which convention is more readable.
History
Traditional typesetting
Shortly after the invention of movable type, highly variable spacing was created, which could create spaces of any size and allowed for perfectly even justification. Early American, English, and other European typesetters' style guides specified spacing standards that were all essentially identical from the 18th century onwards. These guidese.g., Jacobi in the U.K. and MacKellar, Harpel, and De Vinne in the U.S.indicated that sentences should be em-spaced, and that words should be 1/3 or 1/2 em-spaced. The relative size of the sentence spacing would vary depending on the size of the word spaces and the justification needs. For most countries, this remained the standard for published work until the 20th century. Yet, even in this period, there were publishing houses that used a standard word space between sentences.Mechanical type and the advent of the typewriter
Mechanical type systems introduced near the end of the 19th century, such as the Linotype and Monotype machines, allowed for some variable sentence spacing similar to hand composition. Just as these machines revolutionized the mass production of text, the advent of the typewriter around the same time revolutionized the creation of personal and business documents. But the typewriters' mechanical limitations did not allow variable spacingtypists could only choose the number of times they pressed the space bar. Typists in some English-speaking countries initially learned to insert three spaces between sentences to approximate the wider sentence spacing used in traditional printing, but later settled on two spaces, a practice which continued throughout the 20th century. This became known as "English spacing" and marked a divergence from French typists, who continued to use French spacing.Transition to single spacing
In the early 20th century some printers began using one-and-a-half interword spaces to separate sentences. This standard continued in use, to some extent, into the 1990s.Magazines, newspapers, and books began to adopt the single-space convention in the United States in the 1940s and in the United Kingdom in the 1950s. Typists did not move to single spacing simultaneously.
Technological advances began affecting sentence spacing methods. In 1941 IBM introduced the Executive, a typewriter capable of proportional spacing, which had been used in professional typesetting for hundreds of years. This innovation broke the hold that the monospaced font had on the typewriter, reducing the severity of its mechanical limitations. However, this innovation did not spread throughout the typewriter industry; the majority of mechanical typewriters, including all the widely distributed models, remained monospaced, while a small minority of special models carried the innovations. By the 1960s electronic phototypesetting systems ignored runs of white space in text. This was also true for the World Wide Web, as HTML normally ignores additional spacing, although in 2011 the CSS 2.1 standard officially added an option that can preserve additional spaces. In the 1980s desktop publishing software provided the average writer with more advanced formatting tools.
Modern literature
Typography
Early positions on typography supported traditional spacing techniques in English publications. In 1954 Geoffrey Dowding's book Finer Points in the Spacing and Arrangement of Type underscored the widespread shift from a single enlarged em space to a standard word space between sentences.With the advent of the computer age, typographers began deprecating double spacing, even in monospaced text. In 1989 Desktop Publishing by Design stated that "typesetting requires only one space after periods, question marks, exclamation points, and colons" and identified single sentence spacing as a typographic convention. Stop Stealing Sheep & Find Out How Type Works and Designing with Type: The Essential Guide to Typography both indicate that uniform spacing should be used between words, including between sentences.
More recent works on typography weigh in strongly. Ilene Strizver, founder of the Type Studio, says: "Forget about tolerating differences of opinion: typographically speaking, typing two spaces before the start of a new sentence is absolutely, unequivocally wrong." The Complete Manual on Typography states that "The typewriter tradition of separating sentences with two-word spaces after a period has no place in typesetting" and that the single space is "standard typographic practice". The Elements of Typographic Style advocates a single space between sentences, noting that "your typing as well as your typesetting will benefit from unlearning this quaint Victorian habit."
David Jury's book About Face: Reviving the Rules of Typography clarifies the contemporary typographic position on sentence spacing:
Style and language guides
Style guides
Early style guides for typesetting used a wider space between sentences than between words: "traditional spacing", as shown here. During the 20th century, style guides commonly mandated two spaces between sentences for typewritten manuscripts, which were used prior to professionally typesetting the work. As computer desktop publishing became commonplace, typewritten manuscripts became less relevant and most style guides stopped making distinctions between manuscripts and final typeset products. In the same period, style guides began changing their guidance on sentence spacing. The 1969 edition of the Chicago Manual of Style used em spaces between sentences in its text; by the 2003 edition it had changed to single sentence spacing for both manuscript and print. By the 1980s the United Kingdom's Hart's Rules had shifted to single sentence spacing. Other style guides followed suit in the 1990s. Soon after the beginning of the 21st century, the majority of style guides had changed to indicate that only one word space was proper between sentences.Modern style guides provide standards and guidance for the written language. These works are important to writers, since "virtually all professional editors work closely with one of them in editing a manuscript for publication". Late editions of comprehensive style guides, such as the Oxford Style Manual in the United Kingdom and the Chicago Manual of Style in the United States, provide standards for a wide variety of writing and design topics, including sentence spacing. The majority of style guides now prescribe the use of a single space after terminal punctuation in final written works and publications. A few style guides allow double sentence spacing for draft work, and the Gregg Reference Manual makes room for double and single sentence spacing based on author preferences. Web design guides do not usually provide guidance on this topic, as "HTML refuses to recognize double spaces altogether". These works themselves follow the current publication standard of single sentence spacing.
The European Union's Interinstitutional Style Guide indicates that single sentence spacing is to be used in all European Union publications. For the English language, the European Commission's English Style Guide states that sentences are always single-spaced. The Style Manual: For Authors, Editors and Printers, first published in 1966 by the Commonwealth Government Printing Office of Australia, stipulates that only one space is used after "sentence-closing punctuation" and that "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."
National languages not covered by an authoritative language academy typically have multiple style guides, only some of which may discuss sentence spacing. This is the case in the United Kingdom. The Oxford Style Manual and the Modern Humanities Research Association's MHRA Style Guide state that only single spacing should be used. In Canada both the English- and French-language sections of the Canadian Style, A Guide to Writing and Editing, prescribe single sentence spacing. In the United States, many style guides, such as the Chicago Manual of Style, allow only single sentence spacing. The most important style guide in Italy, Il Nuovo Manuale di Stile, does not address sentence spacing, but the Guida di Stile Italiano, the official guide for Microsoft translation, tells users to use single sentence spacing "instead of the double spacing used in the United States".