from dictionary.reference.com: Problem: any question or matter involving doubt , uncertainty, or difficulty. Challenge: something that by its nature or character serves as a call to battle, contest, special effort, etc.: "Detours, challenges, and crisis, are simply covers for miracles that had no other way of reaching you. - Mike Dooley Problem and Challenge: two words that are strikingly similar yet imply a different call to action. It seems to me, by the definition of these words, that a "problem" often is the first stage of what inevitably can become a "challenge." To me, a "problem" implies something often negative; an invisible wall that has no immediate sense of a solution. A "challenge" goes a step further. Yes, the invisible wall is there, but instead of just saying "oh no, the...