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In writing and typography a ligature occurs where two or more letter-forms are joined as a single glyph. Ligatures usually replace two sequential characters sharing common components, and are part of a more general class of glyphs called "contextual forms" where the specific shape of a letter depends on context such as surrounding letters or proximity to the end of a line.

Contents 1 History 2 Latin alphabet 2.1 Stylistic ligatures 2.2 German ß 2.3 Letters and diacritics originating as ligatures 2.4 Symbols originating as ligatures 2.5 Digraphs 2.6 Latin languages that use special ligatures 3 Non-Latin alphabets 4 Computer typesetting 5 Notes and references 6 See also 7 External links

[edit] History

At the origin of typographical ligatures is the simple running together of letters in manuscripts. Already the earliest known script, Sumerian cuneiform, includes many cases of character combinations that over the script's history gradually evolve from a ligature into an independent character in its own right. Ligatures figure prominently in many historical scripts, notably the Brahmic abugidas, or the bind rune in Migration Period Germanic inscriptions.

Medieval scribes, writing in Latin, conserved space and increased writing speed by combining characters and by introduction of scribal abbreviation. For example, in blackletter, letters with right-facing bowls (b, o, and p) and those with left-facing bowls (c, e, o, and q) were written with the facing edges of the bowls superimposed. In many script forms characters such as h, m, and n had their vertical strokes superimposed. Scribes also added special marks called "scribal abbreviations" to avoid having to write a whole character "at a stroke". Manuscripts in the fourteenth century employed hundreds of such abbreviations.

It should be noted that in writing, a ligature is made by joining two or more characters in a way they wouldn't usually be, either by merging their parts, writing one above another or one inside another; while in printing, a ligature is a group of characters that is typeset as a unit, and the characters don't have to be joined - for example, in some cases fi ligature prints letters f and i more separated than when they are typeset as separate letters.

When printing with movable type was invented around 1450,^[1] typefaces included many ligatures. However they began to fall out of use with the advent of the wide use of sans serif machine-set body text in the 1950s and the development of inexpensive phototypesetting machines in the 1970s, which did not require journeyman knowledge nor training to operate. One of the first computer typesetting programs to take advantage of computer driven typesetting (and later laser printers) was the TeX program of Donald Knuth (see below for more on this). This trend was further strengthened by the desktop publishing revolution around 1985. Early computer software in particular (except for TeX) had no way to allow for ligature substitution (the automatic use of ligatures where appropriate), and in any case most new digital fonts did not include any ligatures. As most of the early PC development was designed for and in the English language, which already saw ligatures as optional at best, a need for ligatures was not seen. In essence, the use of ligatures dropped as the number of employed traditionally trained hand compositors and hot metal typesetting machine operators dropped.

With the increased support for other languages and alphabets in modern computing, and the resulting improved digital typesetting techniques such as OpenType, ligatures are slowly coming back in use.

[edit] Latin alphabet

[edit] Stylistic ligatures

Many ligatures combine f with an adjacent letter. The most prominent example is fi (or fi, rendered with two normal letters). The dot above the i in many typefaces collides with the hood of the f when placed beside each other in a word, and are combined into a single glyph with the dot absorbed into the f. Other ligatures with the letter f includes fi, fj,^[2] fl, ff, ffi, ffl, and specific Slovak ligature fľ (and in theory also ffľ, fĺ, ffĺ). Ligatures for fa, fe, fo, fr, fs, ft, fu, fy, and for f followed by a full stop, comma, or hyphen, as well as the equivalent set for the doubled ff and fft are also used, if less common.

Sometimes, a ligature crossing the boundary of a composite word (e.g., ff in "shelfful"^[3]) is considered undesirable, and computer programs (such as TeX) provide a means of suppressing ligatures.

Some fonts include an fff ligature (the Requiem Italic font by Jonathan Hoefler contains even an fffl ligature), intended for German compound words like Sauerstoffflasche "oxygen tank", Schifffahrt "boat trip" (the latter word is only written with fff if the writer follows the spelling reform of 1996). Official German orthography as outlined in the Duden however prohibits ligatures across composition boundaries, and since the sequence fff in German only ever occurs across such boundaries (Schiff-fahrt, Sauerstoff-flasche), these ligatures cannot be correctly employed for German.^[4]

[edit] German ß

Main article: ß

The German esszett ligature (also called scharfes s (sharp s)), ß evolved from the ligature "long s over round s" or "long s and z". Even though "long s" ſ has otherwise disappeared from German orthography, ß is still considered a ligature, and is replaced by SS in capitalized spelling and in alphabetic ordering.

[edit] Letters and diacritics originating as ligatures

As the letter W is an addition to the Latin alphabet which originated in the seventh century, the phoneme it represents was formerly written in various ways. In Old English the Runic letter Wynn (Ƿ) was used, but Norman influence forced Wynn out of use. By the 14th century, the "new" letter W, originated as two Vs or Us joined together, developed into a legitimate letter with its own position in the alphabet. Because of its relative youth compared to other letters of the alphabet, only a few European languages (English, Dutch, German, Polish, and Welsh) use the letter in native words.

The character Æ (æ, or aesc) when used in the Danish, Norwegian, or Icelandic languages, or Old English, is not a typographic ligature. It is a distinct letter—a vowel—and when alphabetised, is given a different place in the alphabetic order, rather than coming between ad and af. In modern English orthography Æ is not considered an independent letter but a spelling variant, for example: "encyclopædia" versus "encyclopaedia" or "encyclopedia".

Æ comes from classical Latin literature, where it is an optional ligature in some words, for example, "Æneas". It is still found as a variant in English and French, but the trend has recently been towards printing the A and E separately.^[5] Similarly, Œ and œ, while normally printed as ligatures in French, can be replaced by component letters if technical restrictions require it.

In German orthography, the umlaut vowels, ä ö ü historically arose from ae, oe, ue ligatures (strictly, from superscript e, viz. a ͤ, o ͤ, u ͤ). It is still acceptable to replace them with ae, oe ue digraphs when the diacritics are unavailable, while in alphabetic order, they are equivalent not to ae, oe, ue, but to simple a, o, u (except in phone books), unlike the convention in Scandinavian languages, where the umlaut vowels are treated as independent letters with positions at the end of the alphabet.

The ring diacritic used in vowels such as å likewise originated as an o-ligature.^{[citation needed]} The uo ligature ů in particular saw use in Early Modern High German, but it merged in later Germanic languages with u (e.g. MHG fuosz, ENHG fuͦß, Modern German Fuß "foot"). It survives in Czech, where it is called kroužek.

The tilde diacritic as used in Castillian and Portuguese, now representing a "ny" sound and nasalization of the afflected vowel or consonant respectively, originated as an n-ligature.^{[citation needed]}

The letter hwair (ƕ), only used in transliteration of the Gothic language, resembles a hw ligature. It was introduced by philologists around 1900 to replace the digraph hv formerly used to express the phoneme in question, e.g. by Migne in the 1860s (Patrologia Latina vol. 18).

Though a stylistic ligature in German (appearing to this day on street signs for city squares ending in "-platz"), a ligature of t and z was a single letter in the Colonial orthography of the Yucatec Maya language.^[6]

[edit] Symbols originating as ligatures

The most common ligature is the ampersand &. This was originally a ligature of E and t, the Latin word for "and". It has exactly the same use (except for pronunciation) in French, and is used in the English language. The ampersand comes in many different forms. Because of its ubiquity it is generally no longer considered a ligature, but a logogram.

Like many other ligatures, it has at times been considered a letter (e.g. in early Modern English). In English it is pronounced "and", not "et". Similarly, the Dollar sign, $, probably originated as a ligature but is now a logogram.^[7]

[edit] Digraphs

Digraphs, such as ij in Dutch and ll in Castillian or Welsh, are not ligatures in the general case as the two letters are displayed as separate glyphs: although written together, when they are joined in handwriting or italic fonts the base form of the letters is not changed and the individual glyphs remain separate. Like some ligatures discussed above, these digraphs may or may not be considered individual letters in their respective languages. Until the 1994 spelling reform, the digraphs ch and ll were considered separate letters in Castillian for collation purposes.

Uppercase and lowercase IJ are often available as a single glyph with a distinctive ligature in several professional fonts (e.g. Zapfino). Sans serif uppercase IJ glyphs, popular in the Netherlands, use a typical ligature consisting of a U with a break in the left-hand stroke.

[edit] Latin languages that use special ligatures

• Danish and Norwegian
• French
• German
• Icelandic
• Swedish

[edit] Non-Latin alphabets

See also Complex Text Layout.

Ligatures are not limited to Latin script.

• A number of ligatures have been employed in the Greek alphabet, in particular a combination of omicron (Ο) and upsilon (Υ) which later gave rise to one of the letters of the Cyrillic alphabet — see Ou (letter).
• Cyrillic ligatures: Љ, Њ, Ы, Ѿ. Iotified Cyrillic letters are ligatures of the early Cyrillic decimal I and another vowel: ІА (not in Unicode, ancestor of Я), Ѥ, Ѩ, Ѭ, Ю (descended from another ligature, Оу or Ѹ, an early version of У). Two letters of the Macedonian and Serbian Cyrillic alphabets, lje and nje (љ, њ), were developed in the nineteenth century as ligatures of Cyrillic El and En (л, н) with the soft sign (ь).

• Some forms of the Glagolitic script, used from Middle Ages to the 19th century to write some Slavic languages, have a box-like shape that lends itself to more frequent use of ligatures.
• The Arabic alphabet, historically a cursive derived from the Nabataean alphabet, most letters take a variant shape depending on which they are followed (word-initial), preceded (word-final) or both (medial) by other letters. For example, Arabic mīm, isolated م, tripled (mmm, rendering as initial, medial and final): ممم . Notable are the shapes taken by lām + ʼalif ﻻ, and ʼalif + lām ﻼ. Unicode has a special Allah ligature at U+FDF2: ﷲ.
• The Brahmic abugidas make frequent use of ligatures in consonant clusters. The number of ligatures employed may be language-dependent, thus in Devanagari, many more ligatures are conventionally used when writing Sanskrit than when writing Hindi.

[edit] Computer typesetting

TeX is an example of a computer typesetting system that makes use of ligatures automatically. The Computer Modern Roman typeface provided with TeX includes the five common ligatures ff, fi, fl, ffi, and ffl. When TeX finds these combinations in a text it substitutes the appropriate ligature, unless overridden by the typesetter. Opinion is divided over whether it is the job of writers or typesetters to decide where to use ligatures.

The OpenType font format includes features for associating multiple glyphs with a single glyph, used for ligature substitution. Typesetting software may or may not implement this feature, even if it is explicitly present in the font's metadata. XeTeX is a TeX typesetting engine designed to make the most of such advanced features. This type of substitution used to be needed mainly for typesetting Arabic texts, but ligature lookups and substitutions are being put into all kinds of Western Latin OpenType fonts.

This table shows discrete letter pairs on the left, the corresponding Unicode ligature in the middle column, and the Unicode code points on the right. Provided you are using an operating system and browser that can handle Unicode, and have the correct Unicode fonts installed, some or all of these will display correctly. See also the provided graphic.

Ligatures in Unicode

Non-Ligature	Ligature	Unicode
Et	&	U+0026
ss	ß	U+00DF
AE, ae	Æ, æ	U+00E6, U+00C6
OE, oe	Œ, œ	U+0152, U+0153
Ng, ng	Ŋ, ŋ	U+014A, U+014B
fŋ	ʩ	U+02A9
ue	ᵫ	U+1D6B
ff	ff	U+FB00
fi	fi	U+FB01
fl	fl	U+FB02
ffi	ffi	U+FB03
ffl	ffl	U+FB04
ſt	ſt	U+FB05
st	st	U+FB06

[edit] Notes and references

[edit] See also

• Category:Latin alphabet ligatures
• Sigla
• Complex text layout
• List of words that may be spelled with a ligature

[edit] External links

• Blogdorf on ligatures
• Decline and Fall of the Ligature: I Love Typography
• Hoefler & Frere-Jones Requiem font
• Emigre: Mrs Eaves ligatures

The ISO basic Latin alphabet
Aa	Bb	Cc	Dd	Ee	Ff	Gg	Hh	Ii	Jj	Kk	Ll	Mm	Nn	Oo	Pp	Qq	Rr	Ss	Tt	Uu	Vv	Ww	Xx	Yy	Zz
history • palaeography • derivations • diacritics • punctuation • numerals • Unicode • list of letters

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