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.