ō⁵, interj. An exclamation, often of surprise, sudden recognition or comprehension.

I a‘a ana koe i nana‘i? Ō! Nō te tautai mātou.
What were you up to yesterday? Oh! we went fishing;

Ō! Kāre rava au i kite ē ka ‘akapē‘ea.
Oh! I don’t know what to do at all.