Formal/Respectful:
* Kānaka maikaʻi: This literally translates to "good man" and conveys respect and good character. It's a very general term, but it can be used in situations where you want to show courtesy.
* Aliʻi: This means "chief" or "noble" and implies a sense of leadership and authority. It's a very formal term and should be used with caution.
Informal/Casual:
* Kanaka: This simply means "man" or "person" and is a more informal way to address someone.
* E komo mai: This means "welcome" and can be used as a polite greeting.
* Aloha kākou: This is a general greeting that can be used to address a group of people, including gentlemen.
Ultimately, the best way to address a gentleman in Hawaiian will depend on the specific context and the relationship you have with the person.