@@@ per Lokyt, the verb might be hlara- since the root SLAS is substantival
Quenya
hlar-
verb. hear
hlar-
verb. to hear
hlas
noun. ear
The Quenya word for “ear” is derived from primitive √S-LAS, an elaboration of √LAS “listen” (PE17/62, 77). It had a stem form of hlar- because medial s generally became z and then r, but the s was preserved when final.
Conceptual Development: In The Etymologies of the 1930s the word for “ear” was derived directly from ᴹ√LAS “listen”, and had the form lár (Ety/LAS²). This seems to be a brief reversion to Early Qenya phonology of the 1910s, where medial s survived and it was final s that became r (PE12/26); compare to ᴹQ. kár (kas-) “head”, also from The Etymologies (Ety/KAS). In that document, the Noldorin word for “ear” was N. lhewig, a singular form based on the fossilized dual lhaw (Ety/LAS²). The voiceless lh- in this word was the result of the Noldorin sound-change of the 1930s whereby ancient initial r-, l- were unvoiced.
This Noldorin word made it into Lord of the Rings drafts as part of Amon Lhaw “Hill of Hearing, (lit.) Hill of Ears” (TI/364), a form that Tolkien retained in the published version (LotR/393). Since the unvoicing of initial l was no longer a feature of Sindarin of the 1950s and 60s, Tolkien needed to contrive a new derivation from primitive √S-LAS, which also necessitated a change in the Quenya cognate to voiceless initial hl-.
Early Qenya words for “ear” from the 1910s had a completely different basis. They include ᴱQ. ankar (ankas-) “ear (of men)”, ᴱQ. qan (qand-) “ear”, and ᴱQ. unk (unq-) “ear (of animals)” from the Qenya Lexicon, all based on the root ᴱ√ṆQṆ (QL/31, 76, 98). The last of these reappeared as unko “ear” in the Early Qenya Grammar of the 1920s and contemporaneous word lists (PE14/52, 76, 117; PE15/71), but seems to have been abandoned by the 1930s.
hlas
ear
hlas noun "ear", stem hlar- as in the dual form hlaru (PE17:62). Compare lár #2.
lár
ear
lár (2) noun "ear" (?). Tolkien's wording is not clear, but ¤lasū is given as an ancient dual form "(pair of) ears"; Quenya lár could represent the old singular las- (LAS2). In a post-LotR source, Tolkien derives hlas "ear" (dual hlaru) from a stem SLAS(PE17:62). Initial hl- rather than l- reflects the revised form of the stem (LAS becoming SLAS), and in the later version of the phonology, postvocalic -s does not become -r when final. Compare the noun "dream", given as olor in the Etymologies (LOS), but as olos pl. olori in a later source (UT:396)
ten-
verb. hear
ten- (4) vb. "hear", future tense tenuva (MC:213; in Tolkien's later Quenya, "hear" is hlar-)
hlasta-/lasta-
verb. hear
cár
head
cár (cas-) ("k")noun "head" (KAS).The given stem-form appears doubtful within the phonological framework of LotR-style Quenya. Probably we should read cas with stem car- (PE14:69 indeed reads "kas head, pl. kari", and VT49:17 quotes the sg. "kas" from a post-LotR source). Compare other forms found in late sources: hlas "ear" with stem hlar- (PE17:62) and olos "dream", pl. olori (UT:396). In Tolkiens early "Qenya", post-vocalic -s became -r at the end of words but was preserved when another vowel followed. His later scheme either lets -r appear in both positions, or reverses the scenario altogether (hence olos, olor-). It would seem that the forms cár, cas- were distractedly carried over into the Etymologies from the Qenya Lexicon (kar, kas-, QL:45) even though they presuppose an earlier version of the phonology. An apparent variant form in late material, cára from earlier cáza ("k"), however fits the later phonology since intervocalic s would become z > r (PE17:188).
cas
head
cas ("k")"head" (VT49:17), cf. also deleted [cas] ("k")noun "top, summit" (VT45:19). This noun should evidently have the stem-form car-. See cár.
cas
noun. head, head, [ᴱQ.] top, summit
This is the Quenya word for “head”, with a stem form of car- because medial s generally became z and then r, but the s was preserved when final. This word can refer to the head of people and animals, as well as the metaphorical “head” (or top) of other things, in much the same way that Q. tál “foot” can refer to their base.
Conceptual Development: This word was established very early in Tolkien’s writing, being derived from the root ᴱ√KASA “head” all the way back in the Qenya Lexicon of the 1910s (QL/45), but its exact form varied as Tolkien changed his mind on the phonetic development of s in Quenya. Its form in the Qenya Lexicon was in fact ᴱQ. kar (kas-), since in Early Qenya period medial s survived and it was final s that became r (PE12/26). This kar (kas-) was the usual word for head in the 1910s and 20s, but in the typescript version of the Early Qenya Grammar Tolkien instead revised it to ᴱQ. kas (kast-) “head” (PE14/72 and note #5).
In noun declensions from the late 1920s and early 1930s, Tolkien instead had cas (car-), reflecting a conceptual shift in the phonologic development of s (PE13/112-113; PE21/22). However, for reasons unclear, the form ᴹQ. kár (kas-) was restored in The Etymologies written around 1937 under the root ᴹ√KAS “head” (Ety/KEM), despite s > z > r being the normal medial phonetic development in this period (PE19/33). This abnormal form slipped into The Lord of the Rings itself as part of the name Q. Eldacar “Elfhelm” (LotR/1038).
Tolkien generally used the form cas for “head” in his later writings (PE19/103; PE23/49; VT49/17), but in his notes on Words, Phrases and Passages from the Lord of the Rings (WPP) from the late 1950s or early 1960s, Tolkien was forced to contrive another explanation for Eldacar:
> What is -kar in names. How could it stand for helm? E.g. as stem ✱kāsā (√KAS, head) would give kāra, but in compound forms -kāsă > -kas. Would not an ă be lost before voicing of s or at least before z > r (PE17/114).
In this note Tolkien considered having Q. carma “helm” < kas-mā, but discarded the idea since he felt karma “tool or weapon” < KAR “do, make” + mā was the more likely meaning. He then said “Eldă|kāzā in compounds to -kār(ă) > -kar” despite its phonological implausibility, and indeed kāza/kára appeared in a discussion of helms within 1964 notes on Dalath Dirnen (DD: PE17/188).
In Tolkien’s earlier writings the word kas was also frequently translated “top”, such as the glosses “head, top” in Early Qenya Grammar of the 1920s (PE14/79), “top, summit” in the English-Qenya Dictionary of the 1920s (PE15/78), and the early-1930s allative form kasta “up (to the top)” (PE21/22).
Neo-Quenya: I would assume this second meaning “top” survived in Tolkien’s later conception of the language, analogous to English “head of the stairs”. Unlike English, I would not assume cas could be used for “front”, as in “head of the line”.
cára
noun. head
hlar- verb "hear", future tense hlaruva "shall hear" in Markirya. Since the original root is SLAS, this verb may have the past tense *hlassë (for slansē) in more classical forms of Quenya, perhaps re-formed as *hlarnë (or *hlarrë, for hlazze) in spoken Noldorin Quenya. Compare #hriz- "snow" (root SRIS) with past tense hrinsë/hrissë, as well as Tolkien's remarks in PE19:99.