New to medieval genealogy and English history. Difficulty in finding a dictionary of terms. May one be suggested. Expecially what is meant by "membrane" on the Rolls.
A membrane was a skin of vellum or parchment, often large, like an extended sheet of paper, but not of any regulated specific size. These "membranes" were the standard pieces of most charters, letters patent, indentures, court and Pipe rolls, in fact most legal documents of the medieval and early modern period. When several membranes are included, loosely grouped or stitched together, they are usually referred to by numbers -- m1, m2, etc. Hope this helps!
As for medieval dictionaries, there are a few sources online: