Topic summary
Hair space
Extracted from the Wikipedia article Whitespace character.
Hair spaces around dashes
Em dashes used as parenthetical dividers, and en dashes when used as word joiners, are usually set continuous with the text. However, such a dash can optionally be surrounded with a hair space (U+200A) or a thin space (U+2009). The hair space can be written in HTML by using   and the thin space is  . These spaces are much thinner than a normal space (except in a monospaced font), with the hair space in particular being the thinnest of horizontal whitespace characters.