The voiced dental non-sibilant fricative is a type of consonantal sound, used in some spokenlanguages. The symbol in the International Phonetic Alphabet that represents this sound, eth, is ð, and the equivalent X-SAMPA symbol is D. The symbol ð was taken from the Old English letter eth, which could stand for either a voiced or unvoiced interdental fricative. This symbol is also sometimes used to represent the dental approximant, though that is more clearly written with the lowering diacritic, ð̞. The dental fricatives are often called "interdental" because they are often produced with the tongue between the upper and lower teeth, and not just against the back of the teeth, as they are with other dental consonants. It is familiar to English speakers as the th sound in then.
This sound, and its unvoiced counterpart, are actually rare phonemes. Almost all European and Asian languages, such as German, French, Persian, Japanese, and Chinese, lack this sound. Native speakers of those languages in which the sound is not present often have difficulty enunciating or distinguishing it, and replace it with a voiced alveolar fricative or a voiced dental plosive. As for Europe, there seems to be a great arc where this sound (and/or the unvoiced variant) is present. Most of mainland Europe lacks the sound; however, the "periphery" languages of Welsh, English, Spanish, Arabic, some Italian dialects, Greek and Albanian have this phoneme in their consonant inventories.
Its manner of articulation is fricative, which means it is produced by constricting air flow through a narrow channel at the place of articulation, causing turbulence.
Its place of articulation is dental, which means it is articulated with the tongue on either the lower or the upper teeth, or both.
Its phonation type is voiced, which means the vocal cords are vibrating during the articulation.
It is an oral consonant, which means air is allowed to escape through the mouth.
It is a central consonant, which means it is produced by allowing the airstream to flow over the middle of the tongue, rather than the sides.
Carbonell, Joan F. & Joaquim Llisterri (1992), "Catalan", Journal of the International Phonetic Association22 (1-2): 53-56
Cruz-Ferreira, Madalena (1995), "European Portuguese", Journal of the International Phonetic Association25 (2): 90-94
Martínez-Celdrán, Eugenio; Ana Ma. Fernández-Planas & Josefina Carrera-Sabaté (2003), "Castilian Spanish", Journal of the International Phonetic Association33 (2): 255-259
Mateus, Maria Helena & Ernesto d'Andrade (2000), The Phonology of Portuguese, Oxford University Press, ISBN 0-19-823581-X
Thelwall, Robin (1990), "Illustrations of the IPA: Arabic", Journal of the International Phonetic Association20 (2): 37-41
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Where symbols appear in pairs, the one to the right represents a voiced consonant. Shaded areas denote pulmonic articulations judged impossible.
