The 'Ā' and the 'Ō' categoies in te reo Māeori are the cornerstone of the language and also explain a lot abouyt Mārori relationships with the world around them. In some ways there are clear distinctions as to what falls into each category, but there are also some nuances within those categories. It takes a lot of learning, embedding in te ao Māori and practise to really get to grips with them!
The 'Ā' and the 'Ō' categories are something which you must consider with possessives in Māori. In the table below you can see that there are two forms of the possessive pronoun for each person.
Te kawekawe of te wheke (the tentacles of the octopus) is one way to help you learn which words take 'ā'; and which take 'ō'.
Listen also to this taringa podcast for more explanation.
Whakarākei - Adornments (Clothes, taonga, etc).
Whanaunga - Relations (Of the same generation or older - also to note that your hoa belong to ‘O’; including hoa rangatira; except when you refer to your better half as your tāne or wahine, then its ‘A’ category).
Waka - Modes of transport (Where transport is their main purpose e.g not a bulldozer cause its main purpose is its mahi).
Wāhanga - Parts of someone/thing (Body parts, Parts of house, etc).
Whakaruruhau - Shelter (Kāinga, various whare, tari, etc - be careful of things like Umbrella as they are only consider shelter when in use, however when it isn’t it's just a rākau which would be an ‘A’ category, but then again if it's a 'tokotoko' which is like a stick - it';s probably 'ō)'!).
Whakaora - Something beneficial to your wellbeing (Rongoā, Wai māori).
Wāhi - Places (Towns/Cities, Whenua, Marae complex, etc).
Whakaahua - Adjectives, Qualities of something/someone (Te ātaahua hoki o tōku hoa rangatira, te tawhito o te whare, etc).