D with stroke based on D
Đ (lowercase: đ, 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 đ is based on the straight-backed roman d, like in  Sámi Languages and  Vietnamese. Crossed d is a letter in the alphabets of several languages and is used in linguistics as a voiced dental fricative.Appearance
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 Đ. 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.Latin
Đ was used in Medieval Latin to mark abbreviations of words containing the letter d. For example, hđum could stand for heredum "of the heirs". Similar crossbars were added to other letters to form abbreviations.South Slavic languages
The crossed d was introduced by the Serbian philologist Đuro Daničić in 1878 for use in Serbo-Croatian in his Dictionary of the Croatian or Serbian Language, replacing the older digraphs dj and gj. Daničić modeled the letter after the Icelandic and Anglo-Saxon letter eth, albeit representing a different sound, the affricate [dʑ]. 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 are heavily influenced by Serbo-Croatian from the Yugoslav period).
The crossed d is today considered a distinct letter, and is placed between Dž and E in alphabetical order. Its Cyrillic equivalent is Ђ ђ. Its partial equivalent in Macedonian is Ѓ ѓ (because only some dialects contain the /dʑ/ sound). When a true đ 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 đ used to be more common in Serbo-Croatian texts, but it is falling out of practice.