one space after a period started in around 1950.
when did one space after a period start?
around 1950
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"the gregg reference manual" is a style manual intended for business professionals. the 1985 edition simply indicated that two spaces were to be used following terminal punctuation. the most recent edition, published in 2005, provides detailed guidance for sentence spacing. its general guidance indicates that, "the standard for proportional fonts has always been the same: use only one space between the period and the start of the next sentence" and "now that the standards of desktop publishing predominate, the use of only one space after the period is quite acceptable with monospace fonts." however, although the author states that one space is correct in draft manuscripts for typesetting and most other instances, certain specific cases might benefit from additional space between sentences. for example, "as a general rule, use one space at the end of a sentence, but switch to two spaces whenever you feel a stronger visual break between sentences is needed." the manual identifies specific instances when only one space is to be used between sentences such as "if you are preparing manuscript on a computer and the file will be used for typesetting, use only one space and ignore the issue of visual appearance." the manual indicates that writers should also "use only one space if the text will have justified margins," and "if the manuscript has already been typed with two spaces at the end of every sentence, use the replace function to change two spaces to one space throughout." the author adds the caveat that in certain instances a writer may want to use two spaces between sentences. the examples given are: when one space "may not provide a clear visual break between sentences", if an abbreviation is used at the end of a sentence, or when some very small proportional fonts (such as 10-point times new roman) are used. the manual clearly places an emphasis on the use of white space to create a pleasing document by noting spacing rules that differ from current norms such as the use of two spaces before opening a parenthesis, after closing quotation marks, and after opening single quotation marks inside of sentences.
sentence spacing in language and style guides