Māori Grammar

Hei can be used to talk about a future location - that is, where someone or something will be.

Hei te marae rātou.
They will be at the marae.

This is the future location marker which is the equivalent of i (where something was located) and kei (where something is now).

Hei can also be used to talk about a "location" in time - that is, when someone or something will be:

Hei āpōpō au tae mai ai.
I will come tomorrow.

Hei tērā Mane rātou tae mai ai.
They arrive next Monday.

It is common to say that someone will do something in the future without hei:

Ka haere ahau ki te hokomaha a tērā wiki.
I will go to the supermarket next week.

But hei... ai is used to emphasise the time (in a similar way to how the agent emphatic emphasises the person doing the action):

Hei tērā wiki ka haere ai au ki te hokomaha.
It will be next week that I will go to the supermarket.