D with stroke different from Ꟈ
Vietnamese
Đ 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 Đ the eighth letter. Đ is a letter in its own right, rather than a ligature or letter-diacritic combination; therefore, đá would come after dù in any alphabetical listing.
Đ represents a voiced alveolar implosive (/ɗ/) or, according to Thompson (1959), a preglottalized voiced alveolar stop (/ʔd/). 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 Đ was later incorporated into Alexandre de Rhodes' seminal Dictionarium Annamiticum Lusitanum et Latinum:
Another letter written with the symbol đ 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 đa đa: partridge. And this letter is very commonly used at the beginning of a word.
On older typewriters, Đ was located where Z would be in the French AZERTY layout. Alternatively, a hyphen can be overstruck onto a D.
On computers without support for a Vietnamese character set or Unicode, Đ is encoded as DD and đ as dd according to the Vietnamese Quoted-Readable standard. Vietnamese computer users typically input Đ as DD in the Telex and VIQR input methods or as D9 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 (0 on a U.S. keyboard) to đ, or Đ when holding down ⇧ Shift. The Windows layout also maps ZA0-11 (=) to ₫.
Other modes of communication also have dedicated representations of Đ. In Vietnamese Braille, it is ⠙, which corresponds to D in French Braille. In the Vietnamese manual alphabet, Đ is produced by touching the thumb to the index finger. In Morse code, it is rendered – · · – · ·, corresponding to Telex's "DD".