A prefix in Definitive Linguistic Notes (DLN) from 1959 meaning “hard, *difficult”, based on the root √SRAG (PE17/154). Tolkien contrasted it with ur(u)- “hard, difficult” from the root √GUR “hard, stiff, difficult, cumbrous, slow”. Examples of its use include hraicénima (or hraicene) “scarcely visible, hard to see” (PE17/154) and {hrainote} “*difficult to count”, the latter appearing unglossed and crossed through on a rejected draft page of these notes (PE17/172).

Neo-Quenya: Although Tolkien did not make it explicit, I believe hrai- implies “hard” due to resistance from the thing or people being worked upon, as opposed to ur(u)- meaning “difficult” due to the inherent complexity of the task; compare hranga- “thwart”.