A typeface (or font family) is a design of letters, numbers and other symbols, to be used in printing or for electronic display. Most typefaces include variations in size (e.g., 24 point), weight (e.g., light, bold), slope (e.g., italic), width (e.g., condensed), and so on. Each of these variations of the typeface is a font.
There are thousands of different typefaces in existence, with new ones being developed constantly.
The art and craft of designing typefaces is called type design. Designers of typefaces are called type designers and are often employed by type foundries. In desktop publishing, type designers are sometimes also called "font developers" or "font designers". (A typographer is someone who uses typefaces to design a page layout.)
Every typeface is a collection of glyphs, each of which represents an individual letter, number, punctuation mark, or other symbol. The same glyph may be used for characters from different scripts, e.g. Roman uppercase A looks the same as Cyrillic uppercase А and Greek uppercase alpha. There are typefaces tailored for special applications, such as cartography, astrology or mathematics.
In professional typography, the term typeface is not interchangeable with the word font (originally "fount" in British English, and pronounced "font"), because the term font has historically been 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, a font came from a type foundry as a set of "sorts", with number of copies of each character included.
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.