UNINTERESTED and DISINTERESTED

Uninterested means not interested.  The audience was uninterested in his boring speech.
Disinterested means impartial or not taking sides. The umpire remained disinterested despite the argument between the players over his decision. This means that the umpire did not side with anyone but still would have been interested in the argument.

Recently this precise use has become confused with uninterested but it is better in written or formal English to keep the meanings separate.