Terminology
In professional typography, the term typeface is not interchangeable with the word font, which was historically defined as a given alphabet and its associated characters in a single size. For example, 8-point Caslon Italic was one font, and 10-point Caslon Italic was another. Historically, fonts came in specific sizes determining the size of characters, and in quantities of sorts or number of each letter provided. The design of characters in a font took into account all these factors.
As the range of typeface designs increased and requirements of publishers broadened over the centuries, fonts of specific weight (blackness or lightness) and stylistic variants (most commonly regular or roman as distinct to italic, as well as condensed) have led to font families, collections of closely related typeface designs that can include hundreds of styles. A font family is typically a group of related fonts which vary only in weight, orientation, width, etc., but not design. For example, Times is a font family, whereas Times Roman, Times Italic and Times Bold are individual fonts making up the Times family. Font families typically include several fonts, though some, such as Helvetica, may consist of dozens of fonts.
The distinction between font and typeface is that a font designates a specific member of a type family such as roman, boldface, or italic type, while typeface designates a consistent visual appearance or style which can be a "family" or related set of fonts. For example, a given typeface such as Arial may include roman, bold, and italic fonts. In the metal type era, a font also meant a specific point size, but with digital scalable outline fonts this distinction is no longer valid, as a single font may be scaled to any size.
The first "extended" font families, which included a wide range of widths and weights in the same general style emerged in the early 1900s, starting with ATF's Cheltenham (1902–1913), with an initial design by Bertram Grosvenor Goodhue, and many additional faces designed by Morris Fuller Benton. Later examples include Futura, Lucida, ITC Officina. Some became superfamilies as a result of revival, such as Linotype Syntax, Linotype Univers; while others have alternate styling designed as compatible replacements of each other, such as Compatil, Generis.
Typeface superfamilies began to emerge when foundries began to include typefaces with significant structural differences, but some design relationship, under the same general family name. Arguably the first superfamily was created when Morris Fuller Benton created Clearface Gothic for ATF in 1910, a sans serif companion to the existing (serifed) Clearface. The superfamily label does not include quite different designs given the same family name for what would seem to be purely marketing, rather than design, considerations: Caslon Antique, Futura Black and Futura Display are structurally unrelated to the Caslon and Futura families, respectively, and are generally not considered part of those families by typographers, despite their names.
Additional or supplemental glyphs intended to match a main typeface have been in use for centuries. In some formats they have been marketed as separate fonts. In the early 1990s, the Adobe Systems type group introduced the idea of expert set fonts, which had a standardized set of additional glyphs, including small caps, old style figures, and additional superior letters, fractions and ligatures not found in the main fonts for the typeface. Supplemental fonts have also included alternate letters such as swashes, dingbats, and alternate character sets, complementing the regular fonts under the same family. However, with introduction of font formats such as OpenType, those supplemental glyphs were merged into the main fonts, relying on specific software capabilities to access the alternate glyphs.
Since Apple's and Microsoft's operating systems supported different character sets in the platform related fonts, some foundries used expert fonts in a different way. These fonts included the characters which were missing on either Macintosh or Windows computers, e.g. fractions, ligatures or some accented glyphs. The goal was to deliver the whole character set to the customer regardless of which operating system was used.
The size of typefaces and fonts is traditionally measured in points; point has been defined differently at different times, but now the most popular is the Desktop Publishing point of 1⁄72 in (0.0139 in/0.35 mm). When specified in typographic sizes (points, kyus), the height of an em-square, an invisible box which is typically a bit larger than the distance from the tallest ascender to the lowest descender, is scaled to equal the specified size. For example, when setting Helvetica at 12 point, the em square defined in the Helvetica font is scaled to 12 points or 1⁄6 in (0.17 in/4.3 mm). Yet no particular element of 12-point Helvetica need measure exactly 12 points.
Frequently measurement in non-typographic units (feet, inches, meters) will be of the cap-height, the height of the capital letters. Font size is also commonly measured in millimeters (mm) and qs (a quarter of a millimeter, kyu in romanized Japanese) and inches.
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