Aspirated stop The digraph was first introduced in
Latin to transliterate the letter
theta in loans from
Greek. Theta was pronounced as an
aspirated stop in
Classical and early
Koine Greek. is used in academic transcription systems to represent letters in south and east Asian alphabets that have the value . According to the
Royal Thai General System of Transcription, for example, represents a series of
Thai letters with the value . is also used to transcribe the phoneme in
Southern Bantu languages, such as
Zulu and
Tswana.
Dental fricatives 's first comic: a German attempts to pronounce English-language "th" sounds (1879) During
late antiquity, the Greek phoneme represented by the letter mutated from an aspirated stop to a
dental fricative , as in
think. This mutation affected the pronunciation of , which began to be used to represent the phoneme in some of the languages that had it. One of the earliest languages to use the digraph this way was
Old High German, before the final phase of the
High German consonant shift, in which and came to be pronounced . In early Old English of the 7th and 8th centuries, the digraph was used until the
Old English Latin alphabet adapted the
runic letter , as well as , a modified version of the Latin letter , to represent this sound. Later, the digraph reappeared, gradually superseding these letters in
Middle English. In
Old and
Middle Irish, was used for as well, but the sound eventually changed into (see below). Other languages that use for include
Albanian and
Welsh, both of which treat it as a distinct letter and alphabetize it between and . English also uses to represent the
voiced dental fricative , as in
this. This unusual extension of the digraph to represent a voiced sound is caused by the fact that, in Old English, the sounds and stood in
allophonic relationship to each other and so did not need to be rigorously distinguished in spelling. The letters and were used indiscriminately for both sounds, and when these were replaced by in the 15th century, it was likewise used for both sounds. (For the same reason, is used in English for both and .) In the
Norman dialect
Jèrriais, the French phoneme is realized as , and is spelled under the influence of English.
Coronal stops Because neither nor were native phonemes in Latin, the Greek sound represented by came to be pronounced . The spelling retained the digraph for etymological reasons. This practice was then borrowed into
German,
French,
Dutch and other languages, where still appears in originally Greek words, but is pronounced . See
German orthography.
Interlingua also employs this pronunciation. In early modern times, French, German and English all expanded this by analogy to words for which there is no etymological reason, but for the most part the modern spelling systems have eliminated this. Examples of unetymological in English are the name of the
River Thames from Middle English and the name
Anthony (though the is often pronounced under the influence of the spelling) from Latin . In English, for can also occur in loan-words from French or German, such as
Neanderthal. The English name
Thomas has initial because it was loaned from
Norman. In the
transcription of Australian Aboriginal languages represents a dental stop, . In the Latin alphabet for the
Javanese language, is used to transcribe the phoneme
voiceless retroflex stop , which is written as in the native
Javanese script.
Lenition Debuccalization In
Irish and
Scottish Gaelic, represents the
lenition of . In most cases word-initially, it is pronounced . For example: Irish and Scottish Gaelic 'will' → 'your will'. This use of digraphs with to indicate lenition is distinct from the other uses which derive from Latin. While it is true that the presence of digraphs with in Latin inspired the Goidelic usage, their allocation to phonemes is based entirely on the internal logic of the Goidelic languages. Lenition in
Gaelic lettering was traditionally denoted in handwriting using an
overdot but typesetters lacked these pre-composed types and substituted a trailing . It is also a consequence of their history: the digraph initially, in Old and Middle Irish, designated the phoneme , but later sound changes complicated and obscured the grapheme–sound correspondence, so that is even found in some words like Scottish Gaelic 'sister' that never had a to begin with. This is an example of "inverted (historical) spelling": the model of words where the original interdental fricative had disappeared between vowels caused to be reinterpreted as a marker of
hiatus.
Neutralization The Irish and Scottish Gaelic lenited is silent in final position, as in
Scottish Gaelic 'tired'. And, rarely, it is silent in initial position, as in Scottish Gaelic 'you'. In English, the in
asthma and
clothes is often silent. ==Graphical variants==