안녕(an-nyeong, annyeong)
A casual greeting used among close friends or younger people, similar to 'hi' or 'hey' in English.
When to use
Among friends, Within family, Among peers
The nuance
Used only among friends, family, or peers; inappropriate in formal situations or with elders.
안녕하세요(an-nyeong-ha-se-yo, annyeonghaseyo)
A polite greeting used to show respect, appropriate for first meetings or addressing elders and strangers.
When to use
Meeting strangers, To elders, Formal occasions
The nuance
Used in formal or respectful contexts, suitable for all ages and relationships.