Middle Primitive Elvish
rin
root. *circle
terēn(ē)
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.
This root first appeared as unglossed ᴱ√RINI in the Qenya Lexicon of the 1910s with derivatives like ᴱQ. rin (rind-) “year, circle” and ᴱQ. rinko “disc, orb, circle” (QL/80). It also had derivatives in the contemporaneous Gnomish Lexicon such as G. rin- “revolve, return, come back; do again” and G. rinc “circular; disc, rondure” (GL/65), but also strengthened forms like G. †drinn “ring, disc” and G. drintha- “to turn (tr.), twist” (GL/30). The root reappeared in The Etymologies of the 1930s with derivatives like ᴹQ. rinda/N. rhenn “circular” and ᴹQ. rinde/N. rhinn “circle” (Ety/RIN).