Middle Primitive Elvish
os
root. round, about
-owo
suffix. masculine suffix
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 Etymologies of the 1930s glossed “round, about”, with various derivatives like N. o “about, concerning” and ᴹQ. osto/N. ost “city, town with wall round” (Ety/OS). Tolkien also considered variant forms ᴹ√OD and ᴹ√OTH, the latter glossed “fort” (EtyAC/OS). This root in The Etymologies is a later iteration of unglossed ᴱ√OSO [’OSO] from the Qenya Lexicon of the 1910s with derivatives like ᴱQ. ossa “wall and moat” and ᴱQ. ostar “township” (QL/71). It also had derivatives in the contemporaneous Gnomish Lexicon such as G. ost “enclosure, yard; town” and G. osta- “to surround with walls, build up; fortify, protect” (GL/63). This early root probably meant something like “✱enclosure”.
In the Quendi and Eldar essay from 1959-60, Q. osto and S. ost were instead derived from the root √SOT “shelter, protect, defend”, but this root has no other derivatives.
Neo-Eldarin: For purposes of Neo-Eldarin, ᴹ√OS “round, about” is too useful to discard, and I prefer it over the later root √SOT, though √(O)S-OT might be salvaged as an extension of √OS.