 Early style guides for typesetting used a wider space between sentences than between words – " traditional spacing " , as shown in the illustration to the right . During the 20th century , style guides commonly mandated two spaces between sentences for <unk> manuscripts , which were used prior to professionally typesetting the work . As computer desktop publishing became commonplace , <unk> 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 ( 1983 ) 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 . 
