Middle Primitive Elvish
per
root. divide in middle, halve
peres
root. affect, disturb, alter
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 “affect, disturb, alter” with derivatives like N. presta- “to affect, trouble, disturb” and N. pesso “it affects, concerns” (Ety/PERES; EtyAC/PERES). It had a short form ᴹ√PER (EtyAC/PERES), but in a separate entry in The Etymologies ᴹ√PER was glossed “divide in middle, halve” (Ety/PER) which doesn’t seem to be related.