Attic η, α_.—Attic has η for original α_ of the earlier period, as φήμη
a. This is true also of the α_ which is the result of early compensative lengthening, by which -ανς-, -ασλ-, -ασμ-, and -ασν- changed to -α_ς-, -α_λ-, -α_μ-, and -α_ν-. (See cross37 b.) But in a few cases like τά_ς for τάνς, and in πᾶσα for πάνσα ( cross113) where the combination ανς arose at a later period, α_ was not changed to η. ὑφᾶναι for ὑφῆναι
b. Original α_ became η after υ, as φυή
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].