Name of Saturday in the seven-day week of the Elves (otsola) in an early word list (PE14/21). The day was related to fire and metals, and was probably derived from sá “fire”.
Qenya
sainen
adverb. *by that means (mentioned)
sa
that [anaphoric]
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.
Early Quenya
sainen
proper name. Saturday
makarnisan
proper name. Saturday
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 correlative ᴹQ. sainen appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/111), a combination of ᴹQ. sa “that [anaphoric]” and the instrumental suffix ᴹQ. -nen.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. sanen “by that means (mentioned)” to be more consistent with the later use of singular instrumentals in correlatives: Q. sinen “by this means”.