وَ«آدَمُ أَبُونَا».
Translation: Adam (peace be upon him) is our father.
آدَمُ: definite proper name, nominative mubtadaʾ.
أَبُو: nominative khabar marked by wāw because it is one of the six special nouns; it is muḍāf to «نَا».
نَا: bound pronoun, genitive muḍāf ilayh.
A predicate may be nominative by a sign other than ḍamma: «أَبُو» takes wāw under its special conditions.