There are actually several ways to say hello in Korean, and the most common ones are Annyeonghaseyo (, formal) and Annyeonghi kaseyo (, informal), as well as Haneul gaseoyo (, sky goodbye, used when parting from someone you know). However, for a more nuanced greeting, you could use Annyeong, which is a combination of Annyeonghaseyo and Heeyeo (, hello). Another option is to use Halmeoni/Halmoni (, grandmother/grandfather) or Oppa/Oppaji (, older brother/older sister), depending on the context. If you want to sound more formal, you could say Gamsahamnida (thank you), which can be used as a greeting as well.