Early Quenya
úva
adjective. the under
(h)úva
pronoun. *his (emphatic possessive)
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
The Qenya Lexicon of the 1910s had the adjective ᴱQ. ūva “the under” under the early root ᴱ√Ū (QL/96).
Neo-Quenya: Luinyelle and Arael coined a neologism ᴺQ. unda “lower, beneath” as an adjectival form of undu “down, under”, posted to the Vinyë Lambengolmor Discord Server (VLDS) on 2022-05-23.