A term for everything in existence, an elaboration on (or variant of) Q. ilu. It was the initial element of Q. Ilúvatar “All-father” (MR/39). In the Quendi and Eldar essay of 1959-60, Tolkien said ilúvë “allness, the all” was an equivalent of Q. Eä “All Creation” (WJ/402). In The Etymologies of the 1930s, it seems to be the equivalent of ᴹQ. ilu “universe” (Ety/IL).
Conceptual Development: In note from the 1940s Tolkien used Ilúve for “heaven” (MR/355), and in the earliest draft of Elendil’s Oath he used Iluve for “world” (SD/56), the latter eventually revised to Q. Ambar (LotR/967). These both seem to have been transient ideas.
Neo-Eldarin: Compared to Q. ilu, I feel that ilúvë is the totality of everything in the universe as originating from Eru, as opposed to ilu which is the entire universe itself. I think that, technically speaking, ilúvë does not include Eru, whereas ilu does. In the sense that it includes all things created by Eru, ilúvë resembles Q. Eä, but it also includes the Ainur and other spirits not within the material realm, and so in that respect is distinct from Ëa. These fine-grained interpretations are mostly speculation on my part.
ilúvë noun "allness, the all". In Ilúvatar "All-father". _(SA; WJ:402, MR:471, IL) _In MR:355, ilúvë seems to be equated with Heaven. Cf. SD:401: Ilúvë Ilu "Heaven, the universe, all that is (with and without the Earth)".