Optical sizes

In metal typesetting, a font is a particular size, weight and style of a typeface. Each font was a matched set of type, one piece (called a "sort") for each glyph, and a typeface consisting of a range of fonts that shared an overall design.

In modern usage, with the advent of digital typography, "font" is frequently synonymous with "typeface", although the two terms do not necessarily mean the same thing. In particular, the use of "vector" or "outline" fonts means that different sizes of a typeface can be dynamically generated from one design. Each style may still be in a separate "font file"—for instance, the typeface "Bulmer" may include the fonts "Bulmer roman", "Bulmer italic", "Bulmer bold" and "Bulmer extended"—but the term "font" might be applied either to one of these alone or to the whole typeface.

The word font (traditionally spelled fount in British English, but in any case pronounced /fɒnt/) derives from Middle French fonte "[something that has been] melted; a casting". The term refers to the process of casting metal type at a type foundry.

In a manual printing (letterpress) house the word "font" would refer to a complete set of metal type that would be used to typeset an entire page. Unlike a digital typeface it would not include a single definition of each character, but commonly used characters (such as vowels and periods) would have more physical type-pieces included. A font when bought new would often be sold as (for example in a Roman alphabet) 12pt 14A 34a, meaning that it would be a size 12-point font containing 14 uppercase "A"s, and 34 lowercase "A"s.

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