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A glyph ( ) is any kind of purposeful mark. In typography, a glyph is "the specific shape, design, or representation of a character". It is a particular graphical representation, in a particular typeface, of an element of written language. A grapheme, or part of a grapheme (such as a diacritic), or sometimes several graphemes in combination (a composed glyph) can be represented by a glyph.
Conversely, in the languages of Western Europe, the dot (formally, tittle) on a lower-case is not a glyph in itself because it does not convey any distinction, and an in which the dot has been accidentally omitted is still likely to be recognized correctly. However, in Turkish language and adjacent languages, this dot is a glyph because that language has two distinct versions of the letter i, with and Dotless I.
In Japanese syllabaries, some of the characters are made up of more than one separate mark, but in general these separate marks are not glyphs because they have no meaning by themselves. However, in some cases, additional marks fulfil the role of , to differentiate distinct characters. Such additional marks constitute glyphs.
Some characters such as in Icelandic and in German may be regarded as glyphs. They were originally typographic ligatures, but over time have become characters in their own right; these languages treat them as unique letters. However, a ligature such as , that is treated in some typefaces as a single unit, is arguably not a glyph as this is just a design choice of that typeface, essentially an feature, and includes more than one grapheme. In normal handwriting, even long words are often written "joined up", without the pen leaving the paper, and the form of each written letter will often vary depending on which letters precede and follow it, but that does not make the whole word into a single glyph.
Older models of required the use of multiple glyphs to depict a single character, as an overstruck apostrophe and full stop to create an exclamation mark. If there is more than one allograph of a unit of writing, and the choice between them depends on context or on the preference of the author, they now have to be treated as separate glyphs, because mechanical arrangements have to be available to differentiate between them and to print whichever of them is required.
In computing as well as typography, the term character refers to a grapheme or grapheme-like unit of text, as found in ( scripts). In typography and computing, the range of graphemes is broader than in a written language in other ways too: a typeface often has to cope with a range of different languages each of which contribute their own graphemes, and it may also be required to print non-linguistic symbols such as . The range of glyphs required increases correspondingly. In summary, in typography and computing, a glyph is a graphical unit.
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