Another alternative form that bugs me for some reason: εννέα and εννιά. In Greek school as a child (long long ago!) I learned nine as εννέα but the Pimsleur course uses εννιά. I just looked it up in Wiktionary and it actually gives a statistic on usage with εννέα being used 75% of the time and εννιά only used 25% of the time. That makes me feel better about sticking with εννέα! I like knowing about the alternate forms so that if I ever do get to go to Greece I will have a better chance of understanding people.