Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Qenya 

rinde

noun. circle

A word for “circle” in The Etymologies of the 1930s under the root ᴹ√RIN (Ety/RIN).

Conceptual Development: The Qenya Lexicon of the 1910s had ᴱQ. rinko “disc, circle, orb” under the early root ᴱ√RINI (QL/80). The contemporaneous Poetic and Mythological Words of Eldarissa had rinko “disc” (PME/80).

Neo-Quenya: For purposes of Neo-Quenya, I would use rindë for “circle” but [ᴺQ.] rinco for “disc”.