óman noun "vowel" (stem omand- as in the pl. omandi, which form was misread as "amandi" in the Etymologies as printed in LR, entry OM; see VT46:7). The terms óma-tengwë, ómëa from a later source are probably to be preferred.
Quenya
óma
voice
óma
noun. voice, resonance of the vocal chords, vowel
óman
vowel
ómëa
vowel
#ómëa noun "vowel" (only pl. ómëar attested); this refers to vowels considered as independent phonemes, according to Fëanor's new insights on phonemics. Also #óma-tengwë. (VT39:8)
óman
noun. vowel
ómëa
noun/adjective. vowel, vowel; [ᴹQ.] voiced
ómataina
ómataina
ómataina, ómataima see óma.
sundóma
base-vowel
sundóma (þ) noun *"base-vowel" (sundo + óma), the determinant vowel of a "base" or root (Christopher Tolkien gives the example KAT, which stem has the sundóma A; the stem TALAT has the sundóma repeated; in derivative forms the sundóma might be placed before the first consonant; e.g. ATALAT) (WJ:319)
tomba
voice / vowel
tomba, also tompë, noun "voice / vowel"; the stem TOM is used of sounds "briefer" than the corresponding stem OM (cf. óma). (PE17:138)
óma-tengwë
vowel
#óma-tengwë noun "vowel" (only pl. óma-tengwi attested); this refers to vowels considered as independent phonemes, according to Fëanor's new insights on phonemics. Also #ómëa. (VT39:8; ómatengwi ["ñ"] with no hyphen in VT39:16)
ómalingwe
voice-???
ómalingwe ?"voice-???" (Narqelion; in Tolkien's later Quenya, óma means "voice" or "vowel" and lingwë means "fish", but at least the latter gloss can hardly be relevant here)
penna
vowel
#penna noun "vowel" (only pl. pennar is attested) (VT39:16)
óma-tengwë
noun. vowel-sign
ómatehta
noun. vowel-sign
óma noun "voice" (OM), "voice, resonance of the vocal chords" (VT39:16), "voice /vowel" _(PE17:138, where it is said that the root _OM refers to "drawn-out" sounds; contrast tomba, q.v.). With pronominal suffix #ómarya "his/her voice", genitive ómaryo "of his/her voice" (Nam, RGEO:67). Instrumental pl. ómainen "with voices" _(WJ:391). Adj. ómalóra "voiceless" (VT45:28)_. The term óma is closely associated with vowels, see óma-tengwë, ómëa; cf. also the compounds ómataina "vocalic extension", the addition to the base a final vowel identical to the stem-vowel (WJ:371, 417; also called ómataima, VT42:24, 25), ómatehtar "vowel-signs", signs used for vowels (usually called simply tehtar, but the latter term strictly includes all kinds of diacritics, not just the vowel-signs) (WJ:396)