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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.
Old English 
The letter thorn was used for writing Old English very early on, as was ð; but, unlike ð, thorn remained in common use through most of the Middle English period. Both letters were used for the phoneme /θ/, sometimes by the same scribe. This sound was regularly realized in Old English as the voiced fricative [ð] between voiced sounds, but either letter could be used to write it; the modern use of [ð] in phonetic alphabets is not the same as the Old English orthographic use. A thorn with the ascender crossed (Ꝥ) was a popular abbreviation for the word that.
Middle and Early Modern English 
The modern digraph th began to grow in popularity during the 14th century; at the same time, the shape of thorn grew less distinctive, with the letter losing its ascender (becoming similar in appearance to the old wynn (Ƿ, ƿ), which had fallen out of use by 1300) and, in some hands, such as that of the scribe of the unique mid-15th century manuscript of The Boke of Margery Kempe, ultimately becoming indistinguishable from the letter Y. By this stage th was predominant, however, and the usage of thorn was largely restricted to certain common words and abbreviations. In William Caxton's pioneering printed English, it is rare except in an abbreviated the, written with a thorn and a superscript E. This was the longest-lived usage, though the substitution of Y for thorn soon became ubiquitous, leading to the common 'ye' as in 'Ye Olde Curiositie Shoppe'. One major reason for this is that Y existed in the printer's type fonts that were imported from Germany or Italy, and thorn did not. The first printing of the King James Version of the Bible in 1611 used the Y form of thorn with a superscript E in places such as Job 1:9, John 15:1, and Romans 15:29. It also used a similar form with a superscript T, which was an abbreviated that, in places such as 2 Corinthians 13:7. All were replaced in later printings by the or that, respectively.
The following were abbreviations during Middle and Early Modern English using the letter thorn:
- – (þe) a Middle English abbreviation for the word the
- – (þt) a Middle English abbreviation for the word that
- – (þu) a rare Middle English abbreviation for the word thou (which was written early on as þu or þou)
- (ys) an Early Modern English abbreviation for the word this
- – (ye) an Early Modern English abbreviation for the word the
- – (yt) an Early Modern English abbreviation for the word that
Modern English 
Thorn in the form of a "Y" survives to this day in pseudo-archaic usages, particularly the stock prefix "Ye olde". The definite article spelled with "Y" for thorn is often jocularly or mistakenly pronounced /jiː/ or mistaken for the archaic nominative case of the second person plural familiar, "ye".
A handwritten form of thorn that was similar to the letter "y" in appearance with a small "e" written above it as an abbreviation for "the" was common in early Modern English. This can still be seen in reprints of the 1611 edition of the King James Version of the Bible in places such as Romans 15:29, or in the Mayflower Compact. The word was never pronounced with a "y" sound, even when so written.
The Icelandic language is the only living language to retain the letter thorn (in Icelandic; þ, pronounced þoddn, [θ̠ɔtn̥] or þordn, [θ̠ɔrtn̥] in common usage). The letter is the 30th in the Icelandic alphabet and never appears at the end of a word. Its pronunciation has not varied much, but in earlier times þ was sometimes used instead of ð as in the word "verþa" which is verða (meaning "to become") in modern Icelandic. Þ was originally taken from the runic alphabet and is described in the First Grammatical Treatise:
|“||Staf þann er flestir menn kalla þ þann kalla ég af því heldur þe að þá er það atkvæði hans í hverju máli sem eftir lifir nafnsins er úr er tekinn raddarstafur úr nafni hans, sem alla hefi ég samhljóðendur samda í það mark nú sem ég reit snemma í þeirra umræðu. Skal þ standa fyrri í stafrófi en titull þó að ég hafi síðar umræðu um hann því að hann er síðast í fundinn, en af því fyrr um titul að hann var áður í stafrófi og ég lét hann þeim fylgja í umræðu eru honum líkir þarfnast sína jartein. Höfuðstaf þe-sins rita ég hvergi nema í vers upphafi því að hans atkvæði má eigi æxla þótt hann standi eftir raddarstaf í samstöfun.||”|
— First Grammarian, First Grammatical Treatise
Constructed languages 
Computing codes 
|Unicode name||LATIN CAPITAL LETTER THORN||LATIN SMALL LETTER THORN|
|Character entity reference||Þ||þ|
Computer keyboarding 
Thorn can be typed on a normal QWERTY keyboard using various system dependent methods. Thorn may also be accessible by copy-and-pasting from a character map, through changing the keyboard layout or through a compose key.
|Computer System||Method for Þ||Method for þ||Notes|
|Compose key ("Multi Key")||Compose ⇧ Shift+T ⇧ Shift+H||Compose t h||Compose is a dead key meaning it is pressed & released rather than held down|
|GTK+||Ctrl+⇧ Shift+u de ↵ Enter||Ctrl+⇧ Shift+u fe ↵ Enter||GTK+ is ISO 14755-conformant for Unicode input|
|Icelandic keyboard||Þ||þ||Can be typed directly|
|Macintosh||⌥ Option+⇧ Shift+T||⌥ Option+t||"U.S. Extended" or "Irish Extended" keyboard layout must be selected|
|UK keyboard (Linux)||Alt Gr+⇧ Shift+P||Alt Gr+p|
|US-International keyboard||Alt Gr+⇧ Shift+T||Alt Gr+t|
|Microsoft Windows||Alt+(0222)||Alt+(0254)||Alt must be held down while the rest of the keys are pressed in sequence. Numbers must be typed on the numeric keypad|
A thorn with a stroke on the ascender (Ꝥꝥ) was used in English (see the section on usage).
A thorn with a stroke on the descender also exists (Ꝧꝧ). The capital form is at codepoint U+A766, and the minuscule form is at codepoint U+A767.
See also 
- First Grammatical Treatise, eText (modernized spelling ed.), NO: Old.
- Freeborn, Dennis (1992) From Old English to Standard English. London: Macmillan
|Wikimedia Commons has media related to: Þ|
- Everson, Michael, All about the letter þorn (blog).
- ————————, "On the status of the Latin letter þorn and of its sorting order", Standards (essay), Evertype.
- "Why is 'ye' used instead of 'the' in antique English?", Oxford English Dictionary's FAQ, Ask Oxford.[dead link]
- Thorn and Eth: how to get them right, Briem.