General "It's okay"
* ʻAʻole pilikia. (pronounced ah-oh-leh pee-lee-kee-ah) - This literally means "no problem."
* Maikaʻi. (pronounced my-kah-ee) - This means "good" or "fine," and can be used as a general "it's okay."
* ʻAʻohe mea. (pronounced ah-oh-heh meh-ah) - This means "nothing," but can also be used to convey "it's okay" in a casual setting.
To express understanding or agreement
* ʻAe. (pronounced ah-eh) - This means "yes."
* Ua maopopo. (pronounced oo-ah mah-oh-poh-poh) - This means "it's clear" or "I understand."
To reassure someone
* ʻAʻole pono e hopohopo. (pronounced ah-oh-leh poh-noh eh ho-poh-poh-poh) - This means "there's no need to worry."
* E noho maluhia. (pronounced eh noh-hoh mah-loo-hee-ah) - This means "be calm" or "stay at peace."
The best phrase to use will depend on the specific situation and the tone you want to convey.