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.
ser-
verb. to rest, repose; to stay, tarry, stop, be for a while, at the moment
-ser
suffix. friend
sermo
noun. friend
seron
noun. friend
-el
suffix. friend
este
feminine name. rest
helde
noun. friend
heldo
noun. friend
helmo
noun. friend
málo
noun. friend
nilmo
noun. friend
sondo
noun. friend
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 verb in The Etymologies of the 1930s appearing as serin “I rest” under the root ᴹ√SED of the same meaning (Ety/SED). It appeared as sére “resteth” in the contemporaneous Fíriel’s Song (LR/72). In the Quenya Verbal System (QVS) of 1948 Tolkien said that ᴹQ. ser- properly meant “to rest, repose”, but it was frequently used to mean “stay, tarry, stop, be for a while, at the moment” (PE22/125). The example he gave was ᴹQ. sinan Elessar Aran __séra__ Arkimbelesse “at present King Elessar is [staying for a while] at Rivendell”.