Eth (Ð, ð; also spelled edh or eð) is a letter used in Old English, Icelandic, Faroese (in which it is called edd), and Dalecarlian. It was also used in Scandinavia during the Middle Ages, but was subsequently replaced with dh and later d. The capital eth resembles a D with a line partially through the vertical stroke. The lowercase resembles an insular d with a line through the top.
The letter originated in Irish writing (Freeborn 1992, 24) as a d with a cross-stroke added. The lowercase version has retained the curved shape of a medieval scribe's d, which d itself in general has not (but see for instance the Audi logo).
In Icelandic, ð represents a voiced dental fricative like th in English "them"; however, the name of the letter is pronounced eþ, i.e., voiceless, unless followed by a vowel. It has also been labeled an "interdental fricative.
In Faroese, ð isn't assigned to any particular phoneme and appears mostly for etymological reasons; however, it does show where most of the Faroese glides are, and when the ð is before r it is in a few words pronounced as [g]. In the Icelandic and Faroese alphabets, ð follows d.
In Old English, ð (referred to as ðæt by the Anglo-Saxons) was used interchangeably with þ (thorn) to represent either voiced or voiceless dental fricatives. The letter ð was used throughout the Anglo-Saxon era, but gradually fell out of use in Middle English, disappearing altogether by about 1300; þ survived longer, ultimately being replaced by the modern digraph th by about 1500.
The ð is also used by some in written Welsh to represent the letter 'dd' (the voiced dental fricative).
Lower-case eth is used as a symbol in the IPA (IPA), again for a voiced dental fricative, and in IPA usage, the name of the symbol is pronounced with the same voiced sound, as /ɛð/. (The IPA symbol for the voiceless dental fricative is θ.)
Prince By-Tor takes the cavern to the North light,
The sign of Eth is rising in the air.