France) that used a standard word space between sentences—a technique called French spacing (illustration below). 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. [ 20 ] 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 spacing—typists 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 [ 21 ] to approximate the wider sentence spacing used in traditional printing, but later settled on two spaces, [ 22 ] a practice that continued throughout the 20th century. [ 6 ] This became known as English spacing, and marked a divergence from French typists, who continued to use French spacing. [ 23 ] In the early 20th century, some printers began using one and a half interword spaces (an " en quad ") to separate sentences. [ 24 ] This standard continued in use into the 1990s. [ 25 ] 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. [ 26 ] Typists did not transition to single spacing simultaneously. The average writer still relied on the typewriter to create text—with its inherent