au
1. (pronoun) I, me - like all pronouns and personals, takes a when following ki, i, kei and hei but does not take a when used as the subject of the sentence, except in some dialects. Never occurs after he, te and ngā and is not used after the prepositions a, o, mā, mō, nā, nō or with tā and tō.
(Te Kākano Textbook (Ed. 2): 13;)
2. (pronoun) we, us - sometimes used as a collective pronoun with this meaning by leaders to refer to their people, especially in classical Māori.
Ko te mea i mahue ai a Muri-whenua i a au, i a Ngāti Whātua, he kōhuru nā Ngāti Kahu-mate-a-ika (Wh4 2004:103) / The reason that we, Ngāti Whātua, left Muri-whenua was a treacherous deed perpetrated by Ngāti Kahu-mate-a-ika.
