Kei te mokemoke au.
I am lonely.
- this is an example of a stative sentence
au and ahau are interchangeable, except that in cases where we would write a au, the a is omitted if ahau is used, for example,
Kei te titiro ia ki a au.
Kei te titiro ia ki ahau.
He's looking at me.
- this is an example of an active sentence