* Επόπτης (Epóptēs): This is probably the closest single word. It implies overseeing and watching over, often with a sense of authority and responsibility. It's suitable for supervisors in many fields.
* Επιβλέπων (Epiblépōn): This word means "overseeing" or "supervising" and is often used as a participle, meaning it's used descriptively rather than as a noun. You might see it used as a title, but it's less common than `Επόπτης`.
* Διευθυντής (Dieuthuntís): This translates to "director" or "manager" and is a more senior position than a supervisor. It could be appropriate depending on the level of responsibility.
* Προϊστάμενος (Proïstámenos): This means "foreman" or "superintendent," and suggests someone in charge of a team or project.
The best choice will depend on the specific context. For a general supervisor, Επόπτης (Epóptēs) is likely the most accurate.