? (lowercase: ?, Latin alphabet), known as crossed D or dyet, is a letter formed from the base character D/d overlaid with a crossbar. Crossing was used to create eth (ð), but eth has an uncial as its base whereas ? is based on the straight-backed roman d. Crossed d is a letter in the alphabets of several languages and is used in linguistics as a phonetic symbol.
In the lowercase, the crossbar is usually drawn through the ascender, but when used as a phonetic symbol it may be preferred to draw it through the bowl, in which case it is known as a barred d. In some African languages' orthographies, such as that of Moro, the barred d is preferred.
In the uppercase, the crossbar normally crosses just the left stem, but in Vietnamese and Moro it may sometimes cross the entire letter.
The DE ligature should not be confused with the ?. That ligature was used stylistically in pre-19th century Spanish as a contraction for de, as a D with an E superimposed. For example, Universidad DE Guadalajara.
A lowercase ? appeared alongside a lowercase retroflex D in a 1982 revision of the African reference alphabet. This revision of the alphabet eliminated uppercase forms, so there was no conflict between ? and ?.
? was used in Medieval Latin to mark abbreviations of words containing the letter d. For example, h?um could stand for heredum "of the heirs". Similar crossbars were added to other letters to form abbreviations.
The crossed d was introduced by Serbian philologist ?uro Dani?i? in 1878 for use in Serbo-Croatian in his Dictionary of the Croatian or Serbian Language, replacing the older digraphs dj and gj. Dani?i? modeled the letter after the Icelandic and Anglo-Saxon letter eth, albeit representing a different sound, the affricate . In 1892 it was officially introduced in Croatian and Slavonian schools (in the Habsburg Kingdom of Croatia-Slavonia where the Croatian language was official) and so definitively added to Gaj's Latin alphabet. The letter thereafter gradually entered daily use, spreading throughout Serbo-Croatian and then to Macedonian (its Latin transliterations heavily influenced by Serbo-Croatian from the Yugoslav period).
The crossed d is today considered a distinct letter, and is placed between D? and E in alphabetical order. Its Cyrillic equivalent is ? ?. Its partial equivalent in Macedonian is ? ? (because only some dialects contain the /d?/ sound). When a true ? is not available or desired, it is transcribed as dj in modern Serbo-Croatian, and as gj in Macedonian. The use of dj in place of ? used to be more common in Serbo-Croatian texts, but is now considered obsolete and discouraged by style guides.
? is the seventh letter of the Vietnamese alphabet, after D and before E. Traditionally, digraphs and trigraphs like CH and NGH were considered letters as well, making ? the eighth letter.? is a letter in its own right, rather than a ligature or letter-diacritic combination; therefore, ?á would come after dù in any alphabetical listing.
? represents a voiced alveolar implosive (/?/) or, according to Thompson (1959), a preglottalized voiced alveolar stop (/?d/). Whereas D is pronounced as some sort of dental or alveolar stop in most Latin alphabets, an unadorned D in Vietnamese represents either /z/ (Hanoian) or /j/ (Saigonese).
The Vietnamese alphabet was formally described for the first time in the 17th-century text Manuductio ad Linguam Tunckinensem, attributed to a Portuguese Jesuit missionary, possibly Francisco de Pina or Filipe Sibin. This passage about the letter ? was later incorporated into Alexandre de Rhodes' seminal Dictionarium Annamiticum Lusitanum et Latinum:
Another letter written with the symbol ? is completely different than our own and is pronounced by raising the tip of the tongue to the palate of the mouth, immediately removing it, without in any way touching the teeth, for example ?a ?a: partridge. And this letter is very commonly used at the beginning of a word.-- Manuductio ad Linguam Tunckinensem[note 1]
On computers without support for a Vietnamese character set or Unicode, ? is encoded as
DD and ? as
dd according to the Vietnamese Quoted-Readable standard. Vietnamese computer users typically input ? as in the Telex and VIQR input methods or as in the VNI input method. In the absence of an input method, the TCVN 6064:1995 and Microsoft Windows Vietnamese keyboard layouts map ZA0-09 ( on a U.S. keyboard) to ?, or ? when holding down . The Windows layout also maps ZA0-11 to ?.
Other modes of communication also have dedicated representations of ?. In Vietnamese Braille, it is ?, which corresponds to D in French Braille. In the Vietnamese manual alphabet, ? is produced by touching the thumb to the index finger. In Morse code, it is rendered - · · - · ·, corresponding to Telex's "DD".
The lowercase ? is used in some phonetic transcription schemes to represent a voiced dental fricative [ð] (English th in this). Eth (ð) is more commonly used for this purpose, but the crossed d has the advantage of being able to be typed on a standard typewriter, by overlaying a hyphen over a d.
A minuscule form of the letter, ?, is the symbol of the ng, the currency of Vietnam, by a 1953 decree by H? Chí Minh. The South Vietnamese ng, on the other hand, was symbolized "?.", in majuscule. In Unicode, the Vietnamese ng symbol is properly represented by ₫ DONG SIGN, but đ LATIN SMALL LETTER D WITH STROKE is often used instead. In Vietnamese, the ng sign is written after the amount in superscript, often underlined.
The uppercase eth (Ð) is also now used to symbolize the cryptocurrency Dogecoin. The idea originated in December 2013 on the website Reddit when a user realized that the symbol wasn't currently being used for any other currency, and the community believed it was fitting for Dogecoin.
Dispersity is represented by the symbol ?, and is a measure of the heterogeneity of sizes of molecules or particles in a mixture, referring to either molecular mass or degree of polymerization.
? and ? are encoded in Unicode as U+0110 LATIN CAPITAL LETTER D WITH STROKE and U+0111 LATIN SMALL LETTER D WITH STROKE; in Latin-2, Latin-4 and Latin-10 as D0 and F0 respectively; and, in Latin-6 as A9 and B9 respectively. In PostScript they are Dcroat, Dmacron, Dslash, dcroat, dmacron and dslash. In Unicode, both crossed d and barred d are considered glyph variants of U+0111.
Unicode has a distinct code point for the visually very similar capital eth, Ð, U+00D0, which can lead to confusion.
As part of WGL4, ? and ? can be expected to display correctly even on older Windows systems.
As paraphrased by de Rhodes:...estque vitium linguæ, aliud ? notatur eo signo quia est omninò diversum à nostro & pronunciatur attollendo extremum linguæ ad palatum oris, illamque statim amovendo, absque eo quod ullo modo dentes attingat ut ?a ?a, perdix: & hæc litera est valdè in usu in principio dictionis.
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