unhappy = not happy :-) mad = very angry (can also mean crazy or insane) upset = unhappy but with a feeling of worry or disappointment Hope this helps! - Herman - www.language-database.com

i think that mad is more expressiv than unhappy ... I hope this help..

Just a little..... You are unhappy when your boyfriend leaves you. You get mad when your boyfriend doesn't return your calls. Upset can be used to replace both. It has a slight different tone to unhappy and mad, but has the same meaning.

Yes there is a difference : "unhappy" is when one is not content with something or a situation and it takes a longer span of time .He is unhappy with his life ,means he is not satisfied , which causes feelings of discontent . "mad" couldbe insane or crazy as Herman says or in this context it means rather an advanced state of anger where one could act aggressively or do stupid things . It usually takes an instant or a certain situation ,it is not a longterm state . " She was so mad at him, that she almost broke up with him." "upset" when one is anxious and worried in a certain situation ,it is a short termed feeling . "He got upset when they told him they might not approve his application . :)