Multi-purpose stadiums are a type of stadium designed to be easily used by multiple types of events. While any stadium could potentially host more than one type of sport or event, this concept usually refers to a specific design philosophy that stresses multi-functionality over specificity. It is used most commonly in Canada and the United States, where the two most popular outdoor team sports – gridiron football and baseball – require radically different facilities. Football uses a rectangular field (Canadian football fields are larger than American ones), while baseball is played on a diamond and large outfield. This requires a particular design to accommodate both, usually an oval. While building stadiums in this way means that sports teams and governments can share costs, it also imposes some challenges.