In typography, a fixed space having a height and a width equal to that of the point size. For example, in a 12-point font, an em space is 12 points wide and 12 points high. An em dash is a dash equal to the size of an em in a particular typeface at a particular size. An en is defined as a fixed space half the size of the em. Thus, in 12-point type, an en space would be 6 points wide. (See Fixed Space and Dash.) The em was originally defined as a square the size of a capital letter "M," which extends to the descender line. This definition is no longer accurate.