Frankly, My Dear, I'm Uninterested (disinterested and uninterested)

The difference between these two words lies not only in the prefixes, but in the meaning of the root word. In "disinterested" the root word "interest" refers to
personal advantage, while in "uninterested" it refers to concern. When people err with these words, they usually use the "dis" word when they should be using the "un" word.

The word "disinterested" has these meanings: dispassionate, not taking sides, impartial, neutral, unbiased, objective, unprejudiced, not seeking one's own advantage, not influenced by self-interest, and not having a personal stake in the outcome. This word is used mainly to describe judges, lawyers, referees, umpires, mediators, and others who are expected to be fair. Its meaning is narrow, and its use is infrequent.
Here are some sentences that use "disinterested" correctly:
                     We've hired a referee who's known for being disinterested.
                     The dispute will be handled by a disinterested judge.
                     They chose a disinterested third party to decide.
                     A person who potentially profits from a decision cannot be
                        considered to be a disinterested negotiator.
                     The doctors treated all the victims with disinterested kindness.
                     She was chosen to be the mediator because she was disinterested.


The word "uninterested," in contrast, has a very clear meaning - NOT
INTERESTED! If I'm uninterested in something, I'm unconcerned, indifferent,
not paying attention, and simply without interest.
These sentences use "uninterested" correctly:
                      He was disappointed to learn that his boss was uninterested in
                         his idea.
                      Although she was uninterested in the topic, she patiently endured
                         listening to the lecture.    
                      I told her our plan, but she seemed uninterested.
                     The children were restless because they were uninterested in the
                         lesson.

It's possible to be DISinterested but not UNinterested. Have you ever watched a
great game when you didn't prefer either team? You were interested in the game but had no stake in the outcome. If you go to court, you expect the judge to be DISinterested but never UNinterested in your case.

If any confusion remains, when you're not sure which word to say, choose "uninterested." Don't use "disinterested" unless you're certain that you mean "impartial." You wouldn't want anyone to confuse your objectivity with your
lack of interest.