A word for “sky” in the Gnomish Lexicon of the 1910s, an elaboration of G. lui “blueness” (GL/55).
Gnomish
el
conjunction. or
el(u)m
interjection. think of that!
ilon
noun. sky
luithon
noun. sky
dai
noun. sky
er
adjective. one
gail
noun. star
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.
A word for “sky” in an early name list from the 1910s and appearing in a couple early names: G. Thlim Quing Ilon “✱Folk of the Heavenly Arc” and G. Cris o Teld Quing Ilon “Gully of the Rainbow Roof” (PE13/101, 104), the latter revised to G. Cris Ilbranteloth (LT2/202). In the contemporaneous Gnomish Lexicon, however, G. Ilon was the name of Ilúvatar (GL/50).