Friends?

How do you define a friend?  I have no where to begin.  I use to believe that a friend was someone who simply:  liked me, enjoyed my company, supported me and was someone I trusted without measure.  Now I have to add that a friend also doesn't get jealous but is happy for a friend's success, doesn't have alterior motives but is true through and through.  I think a friend like this is rare.   I also believe I need to spend more time and energy spending moments with the people who have been and continue to be my closest friends.