Rule of Odds

This photo shows three balls. In the middle, there is a dog ball and there are two tennis balls to the left and right of the center ball. The balls are all against a dark background.
This photo shows three objects in the frame. The rule of odds describes how having three objects in the frame can affect the balance compared to having an even number of objects. I put the different ball in the middle surrounded by two tennis balls to draw attention to it.