a written composition, dealing fully and systematically with the principles of some subject of serious importance. The M. Eng. tretis, O. Fr. tretis, or treitis, is a doublet of "treaty," which also meant a discourse or account. Both words are to be referred to Lat. tractare, to treat, handle, frequentative of trahere, tractus, to draw. "Treatise" thus would mean, by etymology, something well handled, nicely made.