The Adûnaic word for the Númenóreans themselves, clearly related to adûn “west” (PE17/18, SD/240). It is attested only in plural forms Adûnâi (normal plural) and Adûnâim (subjective plural). The final vowel of its singular form must be a long â; if it were short, its plural form would be ✱✱Adûnî instead of the attested Adûnâi.
Sindarin
dúnadan
númenórean
(i Núnadan) (Man of the West), pl. Dúnedain (i Ndúnedain) (WJ:378, 386)