I will at least list the ones I know for a fact that are correct that I've heard another person say it or on a movie, TV series or song, read about in some book, or actually studied. Spanish: "Hola" or "Buenas" (formal- a contraction of "buenos dias", "buenas tardes", etc.) Portuguese: "Olá" French: "Salut" (informal) "Bonjour" (formal) Chinese: "Ni hao" (你好) German: "Hallo" (informal) "Guten tag" (formal- like good day) Japanese: "Konnichi wa" Italian: "Ciao" (informal) "Buon giorno/buona sera" (formal- morning/evening) Korean: "Annyong" (informal) "Annyong haseyo" (formal) I'm sure there's more ways to say hello in each of these languages but these are the ones I'm familiar with.

Hyvää päivää (or just "Päivää") - Finnish (a polite version, a casual greeting is "hei", "moi", "terve" etc) God dag - Swedish, Danish, Norwegian Tere päevast - Estonian

In portuguese is "olá" or "oi". In spanish actually is "hola" (only one l).

γειάσου - Greek

ALOHA! .. is how to say "hello" in Hawaiian :)