Early Primitive Elvish
isi
root. *know
isi
root. *(light) snow
gisi
root. *know
iþi
root. *(light) snow
giþi
root. *(light) snow
sana Speculative
root. *know
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 root in the Qenya Lexicon of the 1910s given as √ISI² with derivatives having to do with “light snow” and Gnomish variants ith- and gith- indicating the true primitive form ✱(Ʒ)IÞI (QL/43). There are no signs of this root in Tolkien’s later writing.