A sport consists of a physical and mentally competitive activity carried out with a recreational purpose for competition, for self-enjoyment, to attain excellence, for the development of a skill, or some combination of these. A sport has physical activity, side by side competition, self-motivation and a scoring system. The difference of purpose is what characterises sport, combined with the notion of individual (or team) skill or prowess.
There is much discussion about what exactly defines a sport for dogs. Some issues:
If a human companion isn't actively involved, is it actually a sport? Take greyhound racing, for example, or hunting from, say, a duck blind, from which the dog retrieves the game.
Is any activity a sport? For example, a conformation show, where the handler and dog walk or trot around a ring for a judge to evaluate the dog's appearance and structure.
This list is intended only to represent anything that anyone is likely to refer to as a dog sport, not to argue its validity as sport. Clearly, there are more sports to add to this list: