Yasou is hello in Greek, prounounced gh'A su.

If you want to learn a few words in Greek before your trip: http://www.greece.org/gr-lessons/gr-english/lessons.html Yasou is in Lesson #1: Meeting People

http://www.greece.org/gr-lessons/gr-english/101words.html

Here's a fun site for you: http://www.yasou.org/

Have a great time! Regards, Linda