This letter has long been associated with the Vietnamese language, ever since it switched over to the chữ Quốc ngữ from the traditional Chữ Nôm. In addition to the amount of diacritics and tone marks, the letter Đ is perhaps one of the most iconic in the Vietnamese alphabet. Yet, it is not the only language to have it. So what is this letter, and how is it used in the languages that use it today?

If you search this character up, with ALT+208 for uppercase and ALT+240 for lowercase, very likely you would see this letter referred to as the “D with stroke”. It is also known as the crossed D, or the dyet, and is described as a “d” or “D” overlaid with a crossbar. However, this should not be confused with the letter eth (ð), which shares a rather similar (or identical) looking uppercase letter, but are entirely separate entities.

Its use has included some abbreviations in Medieval Latin, and a revision of the African reference alphabet. While not all letters in the African reference alphabet is used in each African language that uses it, the crossed d does appear in the orthographies of some of these languages, representing various sounds like the retroflex d. So where else can we find this?
Sámi languages

The Sámi languages, or Sami or Saami, are a group of Uralic languages spoken in the far north of Finland, Sweden, Norway, and the extreme northwestern reaches of Russia. Related to Finnish and Estonian, the Sámi languages are spoken by some 30,000 people, with many of these languages facing endangerment, extinction, or are already extinct.

Specifically, the Northern Sámi, Inari Sámi, and Skolt Sámi languages use the crossed d in their respective orthographies to represent the voiced dental fricative sound /ð/. Yes, this sound is represented by the eth in the international phonetic alphabet, and is a distinct letter from the crossed d (and hence should not be confused as such).

South Slavic languages

In the Balkans lie a rather mutually intelligible set of languages spoken primarily in Serbia, Croatia, Bosnia and Herzegovina, Montenegro, and depending on where you stand on the controversy, Kosovo. Together, there are four varieties of this said language known as “Serbo-Croatian”, although this could be expanded to include Bosnian and Montenegrin, which are also standard varieties of Serbo-Croatian.

Today, these varieties use either just the Latin alphabet, or both the Latin and Cyrillic alphabets simultaneously. Specifically, Croatian uses the Latin alphabet only, while Serbian and Bosnian use both the Latin and Cyrillic alphabets. While Montenegrin also uses both alphabets, its speakers have shown preference for the Latin alphabet over the Cyrillic one.

The crossed d used in this alphabet corresponds to the Cyrillic letter ђ (for the uppercase, it is Ђ). It is modelled after the Anglo-Saxon and Icelandic letter eth, despite representing different sounds altogether. The crossed d here represents the voiced alveolo-palatal affricate /d͡ʑ/, which makes something like a “j” sound as you would hear in “jam” or “jeans”. If this letter could not be used when needed, an alternative transliteration of “dj” is used instead.

It should be noted that for a time, the Latin alphabet was also used in Macedonian, representing a similar or identical sound. However, Macedonian has since moved to exclusively use the Cyrillic alphabet. Here, its Cyrillic equivalent is Ѓ ѓ, and has an alternate transliteration of “gj”.

Vietnamese

Now it is time to mention the elephant in the room. Spoken by over 70 million people in Vietnam and beyond, the Vietnamese language is the Austroasiatic language containing the most number of native speakers. With a tonal system and many phonemic vowels, Vietnamese has a lot of diacritics to distinguish between these sounds and tones. However, the line in the crossed d letter is not a diacritic.

The crossed d is the seventh letter of the Vietnamese alphabet, coming in between D and E. The letter D in Vietnamese does not represent the “d” sound we are familiar with in many major European languages. Instead, it makes a /z/ sound in variants closer to those spoken in Hanoi, and /j/ sound in variants closer to those spoken in Ho Chi Minh. Which came as an interesting learning titbit when trying to pronounce Vietnamese names like Duong.

Here, the crossed d represents the voiced alveolar implosive consonant /ɗ/, which to many non-speakers, may sound a bit like the normal /d/ sound. This consonant, unlike the letter “d”, does not really have northern and southern variants in pronunciation. When the crossed d is not recognised in some systems (like those that do not accept special characters), an alternate transliteration “dd” could be used.

So this is pretty much most of where the crossed d letter is used. While we may have missed out on lesser known languages which may use the crossed d, these languages covered are among the more prolific ones with that letter in their respective orthographies.