A prefix translated as “of” (SD/247) and one of the ways that genitive relationships are expressed in Adûnaic (SD/429). According to Tolkien, “it is not a preposition ... it is the equivalent of an inflexion or suffix” (SD/435). As such, it is used to form adjectives from nouns, as anadûni “western, ✱of the West” from adûni “the West”. When following another noun, it is often elided so that the a is lost, as in Ârû ’nAdûnâi “King of the Númenóreans” (SD/429) and Bâr ’nAnadûnê “Lord of Númenor” (SD/428). This elision occurs in most examples, but seems not to happen in some cases:
When the an- is separated from the modified noun: balîk hazad an-Nimruzîr “ships seven of-Nimruzîr” (SD/247).
When the modified nouns is declined into the subjective case: Bârim an-Adûn “Lords of the West” (SD/247).
However, when the subjective noun ends in a vowel, elision still occurs: narîka ’nBâri ’nAdûn “Eagles of the Lords of the West” (SD/251).
Tolkien used a dash to separate an- from the noun to which it is prefixed but omitted the dash when the prefix was elided. Carl Hostetter and Patrick Wynne suggested (AAD/10) that Ad. an- may be related to the Sindarin genitive marker S. na(n) “with, by”