How do you say hi in south Korean?

Answer 1

First of all, there is no such language as "South Korean". North and South Koreans speak the same Korean language. There are some slight differences between their dialects because of the 60+ years estrangement, but these differences are more in complex grammatical arrangements and recent additions to the vocabulary, not concerning most basic words.

However, to answer the question. Hello or Hi in Korean is "Anyong haseyo" (안녕하세요). Sometimes Koreans will shorten this to "Anyong" (안녕), but this is usually reserved for VERY informal situations, such as when speaking to a young child or a best friend. If in doubt, use Anyong haseyo.