Typographic approximation

A typographic approximation is a replacement of an element of the writing system (usually a glyph) with another glyph or glyphs. The replacement may be a nearly homographic character, a digraph, or a character string. An approximation is different from a typographical error in that an approximation is intentional and aims to preserve the visual appearance of the original. The concept of approximation also applies to the World Wide Web and other forms of textual information available via digital media, though usually at the level of characters, not glyphs.

Historically, the main cause of typographic approximation was a low quantity of glyphs (such as letterforms and symbols) available for printing. In the age of World Wide Web and digital typesetting, especially after the advent of Unicode and enormous amount of computer fonts, typographic approximations are usually caused either by low ability of humans to distinguish and find needed symbols or by inadequate replacement patterns in word processors, rather than by lack of available characters.