Measuring Width

Type is also measured in width, or set size. A line of type is measured in ems. An em is equal to the square of the type body. It was originally so called because the type body bearing a letter m is square. For example, a pica em is 12 points wide. A space half as wide as the em is called an en. The length of line required to set the alphabet of small, or lowercase, pica letters is 13 ems. If this alphabet takes more than 13 ems, it is said to be a fat or expanded face. If it takes less space, it is said to be lean or condensed. Letters in small sizes of type must be wider for clearness and durability.

Careful adjustment of leading, or the spacing between the lines, also makes a page easier to read. Leading, like type, is measured in points. The metal strips formerly used for this spacing were called leads and slugs. The typeless type bodies used to add space between types in a line were known as spaces and, when thicker, quads. These terms remain in the professional vocabulary of editors, typesetters, and printers, though the pieces of metal to which they refer are no longer in common use.

Sizes of Type  - Fonts Type Casting by Hand and by Machine

Invention and Spread of Type and Printing First Designs for Roman and Italic Types

Old-Style Types by Garamond and Caslon - Bodoni Originates Modern Types

Trends in the 19th and 20th Centuries - Inexpensive Fonts