Early Primitive Elvish
miri
root. smile
mṛtyṛ
root. smile
iti Speculative
root. precious
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 hypothetical root to explain words in the Gnomish Lexicon such as G. idra “dear, valued, precious” and G. idril “sweetheart”, the latter being the earliest etymology of the name G. Idril (GL/50). For the later etymologies of this name and the possible conceptual evolution of the root, see the entries for √IR “desire” and √IT “glitter, shine, shimmer, twinkle”.