Under which conditions can an umpire change the ball?

An umpire can change the ball when: 1. The ball becomes lost or unfit for play because it is damaged or out of shape. 2. The ball has become wet or unusable due to rain or dew (as agreed by the umpires). 3. The ball is hit out of the ground or is otherwise lost during play. The replacement ball must be of similar wear and condition to the one it replaces.