Thorn or þorn (Þ, þ), is a letter in the Old English, Gothic, Old Norse, and Icelandic alphabets, as well as some dialects of Middle English. It was also used in medieval Scandinavia, but was later replaced with the digraph th, except in Iceland where it survives. The letter originated from the rune ᚦ in the Elder Fuþark, called thorn in the Anglo-Saxon and thorn or thurs ("giant") in the Scandinavian rune poems, its reconstructed Proto-Germanic name being Thurisaz.
It has the sound of either a voiceless dental fricative [θ], like th as in the English word thick, or a voiced dental fricative [ð], like th as in the English word the. Modern Icelandic usage generally excludes the latter, which is instead represented with the letter eth (Ð, ð), however the pronunciation of words beginning with a þ often depends on that word's position within a sentence, being pronounced [θ] if the word is at the beginning of a sentence but [ð] otherwise. Þ in modern Icelandic also has a voiceless allophone [θ], which occurs in certain positions within a phrase.