Funny is an adjective.. Hilarious means very, very, very funny, and is an adjective. Humor is a noun, to have good sense of humor means quality of a person to be able to be funny and tell hilarious jokes.

"funny" and "hilarious" are both adjectives, and "hilarious" means VERY funny. For example, a "funny movie" or a "hilarious movie". "humor" is a noun, so it cannot be used like the other two. You can say a movie contains humor, but you cannot say a "humor movie".

funny and humorous are much the same. But remember that you need to use the same form - humorous, not humour. (I don't use American spellings) Also 'humorous' is a little more formal that 'funny'. Hilarious is 'very funny' or 'very humorous'. So yes, you can use them interchangeably.