Digraphs, ligatures, dipthongs

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Ligatures and digraphs

A ligature joins two characters into a graphically different form. This includes:

  • alternatives such as æ as ae. Whether this is semantically different, or purely stylistic, depends on context, mostly language.
  • typographical. From the days of metal movable type, something with horizontal overhang such as f (a particular problem case) followed by something like an i (or anything else) would look very widely spaced, and take relatively much space.

Compare 'fi' with 'fi'.

On computers, kerning (the spacing between characters, which is now often computed automatically and fairly well) is handled automatically and tends to look good by default.

...but there are details that kerning does not deal with. Say, making fi overlap as fi means the dot on the i may overlap with the f's curl, so there are still reasons to use the ligature fi instead of letters fi,

(See also [1] under the ligatures heading)


While we just put letters next to each other, other writing systems may have less trivial orthography. Interesting examples include various Indic scripts, which may even represent one character with multiple glyphs (e.g. one vowel with separate graphemes) or Arabic(verify). These differences in orthography (how to write) often has little or no semantic implications(verify).

Additional orthographical rules may apply to all ligatures, such as when abbreviating or hyphenating them.



Digraphs (also known as bigraphs and digrams) write a single sound as two characters (that lose that meaning when separated) because a single character for that sound does not exist, is archaic, or not convenient.

Trigraphs and tetragraphs also exist.

Note this deals with sound rather than type or orthography. Some ligatures are also digraphs, some are not. Non-typographical ligatures are often digraph ligatures.


Non-ligature digraphs include sounds that are written as several graphemes, often because there is no specific grapheme for it. For example:

  • 'ch' in English, such as in 'school.' (It is not an allophone of any reduced form or anythings else)
  • dipthongs are essentially vowel-only digraphs. That is, they graphically represent dipthongs sounds.


Digraph ligatures may be phonetically identical spelling variants. In German, ä and ae, ö and oe, ü and ue, and to a slightly lesser extent ß and ss, are equivalents that largely became such because of systems that did not support them like Morse and typewriters(verify). This also caused diaresis and umlaut variations to be joined into the same visual letter.

Note that conversibility depends on language and context. German appearances of ue are only be seen as a ü if they were a single sound, and not e.g. in aktuelle.

Digraph ligatures may also grow to be considered a separate sound, sometimes even have alphabet status. Swedish and Finnish have Å, Ä, and Ö, Norwegian and Danish have Æ, Ø, and Å. Some have unambiguous separated forms, some do not.

In English, there is no particular difference between, for example, encyclopædia, encyclopaedia, both now considered archaic in favour of encyclopedia.


The English w is another historical example, as it originated as 'vv', two Latin Us (which is why its name is double-u). W replaced the Ƿ character (Wynn) in Old English.

Symbols

Ligatured combinations with a specific function are sometimes accepted as symbols - technically becoming logograms. Consider & which came from a ligature of the Latin 'et', and the dollar sign $.


See also