안녕 (annyeong): This is the most common and versatile way to say "hey" in Korean. It can be used in both formal and informal settings, and it is appropriate for use with friends, family, and strangers alike.
안녕하십니까 (annyeonghaseyo): This is a more formal way to say "hey" and is typically used in situations where you are speaking to someone who is older than you or in a position of authority.
야 (ya): This is a more informal way to say "hey" and is typically used among friends or family members. It is not appropriate for use in formal settings or with strangers.
여보 (yeobo): This is a term of endearment that is typically used between spouses or romantic partners. It can also be used in a more general sense to refer to someone who is close to you.
어이 (eoi): This is a more casual way to say "hey" and is often used to get someone's attention. It is not as polite as 안녕 or 안녕하십니까, but it can be used in informal settings.
When using any of these expressions, it is important to consider the context and the relationship you have with the person you are speaking to.