Korean greetings change with the situation
Korean often has a specific set phrase for a specific moment -- meeting, parting, eating, or leaving the house -- rather than one all-purpose greeting. Even a common phrase like "annyeonghaseyo" (μλ νμΈμ) can feel more or less natural depending on whether you are meeting someone for the first time or seeing them again after a while, so learning these situational phrases makes conversations feel much more natural.
Formality level matters as much as the words themselves
Beyond which phrase to use, Korean greetings also shift in politeness level depending on who you are speaking to -- someone older, a stranger, or a close friend. As a general rule, sticking with the more formal "-seumnida/-seyo" style forms shown here is a safe choice with anyone you do not know well or anyone older than you.
Frequently Asked Questions
Is it okay to say μκ³ νμ ¨μ΅λλ€ (sugohasyeosseumnida) to someone senior to me?
It is natural to say to coworkers or people junior to you, but some consider it slightly awkward directed at someone senior, so it is generally safer to use a different greeting in that situation.
Is μμ¬νμ ¨μ΄μ? (Have you eaten?) actually asking whether I have eaten?
Not usually -- it is mostly used as a set, friendly way of asking how someone is doing, similar to "how are you," rather than a literal question about your last meal.