Middle Primitive Elvish
pilin
root. *arrow
kwessē
noun. feather
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.
An unglossed root in The Etymologies of the 1930s with the derivatives ᴹQ. pilin “arrow”; in The Etymologies as recorded by Christopher Tolkien the root was given as ᴹ√PÍLIM (Ety/PÍLIM), but according to Carl Hostetter and Patrick Wynne the root might also be read as ᴹ√PÍLIN (EtyAC/PÍLIM). This root is probably a later iteration of the early root ᴱ√PILI from the Qenya Lexicon of the 1910s, unglossed and with derivatives like ᴱQ. pilin “feather” and ᴱQ. pilna “arrow” (QL/74); it also had derivatives like G. pilon “arrow, dart” from the contemporaneous Gnomish Lexicon (GL/64). Later “feather” words were based on the root ᴹ√KWES (Ety/KWES; LotR/1122), but ᴹQ. pilin remains the best known Elvish word for “arrow”.