Comments for 幻想

This can also be pronounced as "yume," doesn't it?

No, though I'm guessing you've probably seen it in song lyrics with the furigana for ゆめ?

This is a technique when the songwriter wants to focus on a particular meaning of a word by providing the Kanji for it, in this case 幻(げん)想(そう) - fantasy, illusion, vision dream, but prefers the sound of a more generic word, ie 夢(ゆめ)「ゆめ」meaning dream. It's a quite common technique that you see often.