Nostalgic is a word derived from ancient greek. 'Nostos' (Νόστος) means ' the desire to return (to one's homeland)' and 'algos' (Άλγος) means pain. So, you can say 'nostalgia' as a noun is 'the pain caused by the desire to return'. And obviously, nostalgic is it's adjective :)

oops, i forgot a sentence. That could be: (A greek student studying abroad) > Listening to greek folk music makes me feel nostalgic. > I guess my Irish girlfriend turns nostalgic from time to time here in Greece

I don't entirely agree with Norman. Yes, 'nostalgic' means to think about people or things that happened in the past, but it can be happy or sad.

Adjective: nostalgic 1. Unhappy about being away and longing for familiar things or persons

nostalgia means a sentimental longing for things that r past,like- i get very nostalgic on listening to these old musicals