Head-Covering IV: How

 https://www.deracheha.org/head-covering-4-how/

 As we have learned, Rav Moshe Feinstein rules that the Torah-level obligation is to cover at least most of the head . That leaves the amount of hair that can be left uncovered undefined.

In order to define how much hair can be left uncovered, Rav Moshe turns to the Talmud’s discussion of hair as erva! This is surprising, because Rav Moshe usually takes care to distinguish between the matter of erva and the obligation to cover one’s head, and does not consider women’s hair nowadays to be erva.¹⁰