changes are the consequence of sound changes that separate Old Norse from Proto-Norse and Common Germanic (mostly changes to the vowel system). The first ætt was reduced to its first six letters, fuþąrk, losing the g and w runes (the old a rune is transliterated as ą for Old Norse as the phoneme it expressed had become more closed). The second ætt lost the æ and p runes. The j rune was rendered superfluous due to Old Norse sound changes, but was kept with the new sound value of a. The old z rune was kept (transliterated in the context of Old Norse as ʀ) but moved to the end of the rune row in the only change of letter ordering in Younger Futhark. The third ætt was reduced to four runes, losing the e, ŋ, o and d runes. In tabular form: The Younger Futhark became known in Europe as the "alphabet of the Norsemen", and was studied in the interest of trade and diplomatic contacts, referred to as in Frankish Fulda (possibly by Walahfrid Strabo) and "Ogham of the Scandinavians" in the Book of Ballymote. Rune names The names of the 16 runes of the Younger futhark are recorded in the Icelandic and Norwegian rune poems. The names are: fé ("wealth") úr ("iron"/"rain") Thurs ("thurs", a type of entity, see jötunn) As/Oss ("(a) god") reið ("ride") kaun ("ulcer") hagall ("hail") nauðr ("need") ísa/íss ("ice") ár ("plenty") sól ("Sun", personified as a deity—see Sól (Germanic mythology)) Týr ("Týr, a deity") björk/bjarkan/bjarken ("birch") maðr ("man, human") lögr ("sea") yr ("yew") From comparison with Anglo-Saxon and Gothic letter names, most of these names directly continue the names of the Elder Futhark runes. The exceptions to this are: yr which continues the name of the unrelated Eihwaz rune; thurs and kaun, in which cases the Old Norse, Anglo-Saxon and Gothic traditions diverge. Variants The Younger Futhark is divided into long-branch (Danish) and short-twig (Swedish and Norwegian) runes. The difference between the two versions has been a matter of controversy. A general opinion is that the difference was functional, i.e. the long-branch runes were used for documentation on stone, whereas the short-twig runes were in everyday use for private or official messages on wood. Long-branch runes The long-branch runes are the following rune signs: {|border="0" style="font-size:150%;" |- ||||||||||||||||||||||||||||||| |- !f||u||þ||ą||r||k||h||n||i||a||s||t||b||m||l||ʀ |} Short-twig runes In the short-twig runes (or Rök runes), nine runes appear