Definition of hair space in English:

hair space

noun

Printing
  • A very thin space between letters or words.

    • ‘A hair space is used when extremely small spaces are needed.’
    • ‘And there are one or two quotations inside quotations where the outer double quote needs a hair space to set off the immediately following inner single quote.’
    • ‘I'd like to type hair spaces either side of em dashes and wonder whether there was a system-wide shortcut that I could use.’
    • ‘Some writers eschew the use of the em dash - instead, they replace it with the shorter en dash - which is then also surrounded by spaces or hair spaces.’
    • ‘Em dashes look downright stupid without the hair space on either side: normal spaces are much, much too wide, while no space at all makes the text look cramped.’