ui-

prefix. twi-, twi-, [G.] bi-, di-

A prefix for “twi-” appearing in The Etymologies of the 1930s under the root ᴹ√YŪ “two, both” as an element in N. uial “twilight” (Ety/YŪ). Tolkien’s continued use of S. uial “twilight” in his later writings indicates the ongoing validity of this prefix (LotR/1111.2805; PE17/153, 169).

Conceptual Development: The Gnomish Lexicon of the 1910s had G. gwi- “twi-, bi-, di-” based on primitive ᴱ✶u̯i and related to the dual suffix G. -wi (GL/45).