An adjective in the Qenya Lexicon of the 1910s appearing as silda or sildra “slender”, derived from the early root ᴱ√SḶŘḶ [ÞḶÐḶ] (QL/73).
Early Quenya
silda
adjective. gleaming
silda-ránar
in the moon gleaming
sild(r)a
adjective. slender
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 sixteenth line of the Oilima Markirya poem (MC/213). The first word is the adjective silda “gleaming” followed by an inflected form ránar of Rána “Moon”. Gilson, Welden, and Hostetter suggest it might be an idiomatic use of the dative (PE16/85), but I think it might be a variant form of the locative: the r-locative.
Decomposition: Broken into its constituent elements, this phrase would be:
> silda-rána-r = “✱gleaming-moon-in”