Hello./Hi./How are you?/Good afternoon./Good evening./etc...
안녕+ 하세요
안녕하세요
안녕
well-being, peace, health
하세요
you do, do you?, please do
안녕하세요 is the most common way of greeting someone in Korean. This greeting is in Ejon-claen-mal or polite/formal language.
When someone greets you with 안녕하세요, simply greet the person back with 안녕하세요.
안녕하세요 was originally a question asking "Are you doing well", "Are you at peace?", or "Are you living well?", but since it is a very common expression, people began to not expect any special answers in reply.
안녕하세요 is exactly like asking "What's up?" in English, where you don't really expect an honest answer about what's going on.
Honorifics
Levels of politeness in Korean
Two categories of Korean honorifics
Polite/formal language
Casual/intimate/formal language
Sentences that end in -yo or -습니다 are most likely in polite/formal language.
It is better to use polite/formal language because if you use casual/intimate/formal language in a situation where you should use polite/formal language, you might get into trouble.
감사합니다
Thankyou
감사+ 합니다
감사합니다
감사
appreciation, thankfulness, gratitude
합니다
I do, I am doing
감사합니다 is the most common way to politely say "thank you".
In Korean, the expression "thank you" does not include the word "you" because it's easy to guess to whom you are offering thanks.