Use unfortunately to describe an event that is unlucky or bad in some way. Unfortunately, life is full of chances to use this word.
Someone who's fortunate has good luck. Unfortunately is the adverb form of unfortunate — so unfortunately means "unluckily." If someone asks you whether you have to go to work tomorrow when you'd rather go to the beach, you might answer, "Unfortunately." You might also use unfortunately when you give someone bad news, as in "Unfortunately, we cannot accept your dog to obedience class at this time” or “Unfortunately, you have the flu.”