* 선생님 (seonsaengnim): This is a common and respectful term, often used for teachers, professors, or anyone deserving of respect due to their position or age. It's a safe bet in many formal situations.
* 씨 (ssi): This is a polite suffix added to a person's last name. It's equivalent to "Mr.," "Ms.," or "Miss" in English. For example, "김씨 (Kim ssi)" would be "Mr. Kim" or "Ms. Kim." This is generally appropriate for strangers or people you don't know well.
* 님 (nim): This is a honorific suffix that can be added to many nouns, including names, to show respect. It's a more general term of respect than *seonsaengnim*. While you could use "이름님 (Ireum nim)," where "Ireum" is a name, it's less common than using *ssi* with a last name.
* 아저씨 (ajeossi): This means "mister" or "uncle," and is used for older men. Use it cautiously, as it can sound informal or even patronizing depending on the situation and your relationship with the person.
* 아주머니 (ajumma): This is the female equivalent of *ajeossi*, meaning "madam," "auntie," or "Mrs.," and is used for older women. Again, use with caution due to potential informality.
In short, 선생님 (seonsaengnim) or 씨 (ssi) + last name are generally safe and polite choices unless you have a closer relationship with the person. Avoid *ajeossi* and *ajumma* unless you're certain it's appropriate.