In electoral systems, a wasted vote is any vote cast that is not "used" to elect a winner, and so is not represented in the outcome. However, the term is vague and ill-defined, having been used to refer to a wide variety of unrelated concepts and metrics. The way a wasted vote is defined changes the analysis.
A system's waste of votes is seldom imposed on each party equally. More wasted votes for one party and less for another creates a disproportionate chamber of elected members. Elections are often said to mean to produce a micro-copy of the wider society, distortions produced by wasted votes work against that conversion process. However, a system that produces wasted votes may prevent instability caused by many parties being elected to the legislature.