em space

em space (plural em spaces)

1. (typography) A space which has a nominal width of 1 em.

   Synonyms: em quad, mutton quad, quad

   Coordinate terms: en space, no-break space, thick space, thin space, word space, zero-width space

The em quad and the em space are usually synonymous as they both start as a space with a width of 1 em. However, in electronic publishing a few contrast the two by holding that if the font is condensed or expanded to alter the width of the characters, the em quad remains 1 em in width, while the em space is altered in width to the same proportion as the printing characters.

• em dash
• em quad