Something that demonstrates practicality makes good sense. If you choose your new shoes based on their practicality, you'll probably buy a pair of sneakers, rather than knee-high boots with five inch heels.
A person's practicality can also be called common sense, and an object or action's practicality has to do with how efficient or suitable it is. The practicality of doctors carefully washing their hands before surgery is clear, while the practicality of dressing your dog in a ballerina costume is less so. The root of practicality is practical, which in turn comes from the Old French word practique, "fit for action."