Edh is a letter, ð in lowercase and Ð in uppercase, used in Old English (Anglo-Saxon) and present-day Icelandic and Faeroese. The name is also spelt eth, or to be completely correct, eð. The letter had its origin as a d with a cross-stroke added. The lowercase version has retained the flowing shape of a Medieval scribe's d, which d itself has not.
In Icelandic, ð represents a voiced dental fricative, as in th in English "them". In the Icelandic and Faeroese alphabets, ð follows d. In Anglo-Saxon, ð may represent the same sound as in Icelandic, or the voiceless th of "thread", both of which were also represented by thorn (þ). In Middle English, ð was no longer used.
Lowercase edh is used as a symbol in the International Phonetic Alphabet, again for a voiced dental fricative.