will i lose os x?

i have decided to try using ubuntu on my macbook air, but before i do there is one thing i cannot find an answer to.
i am planning to use the "erase disk and install ubuntu" option, so i will not be duel booting. So my question is, if i decide to go back to os x, can i do that? can i reinstall os x?
Sorry if this is a very dumb question, i have tried googling this for ages and cannot find a straight answer.
Thanks for the help