𐰀𐰴

The long vowel is well supported. Erdal notes that several runiform manuscripts use an explicitly written vowel sign to distinguish long ā and specifically lists a:k “white”; comparative evidence, especially Turkmen /aːk/, confirms the length.

The historical relationship between a:k and ürüŋ is best understood as that of two overlapping Old Turkic terms for “white”, with a:k particularly prominent in early animal-colour terminology.