U.S. Visas may be issued in a variety of circumstances, and may be classified as either immigrant visas or non-immigrant visas. Generally, non-immigrant visas far outnumber immigrant visas on a yearly basis; this type of visa is issued to permit a foreign national to travel to the U.S. for a limited period of time, usually for business, vacations, or to attend school, with the intention that the foreign national will return to his or her native country upon the expiration of the visa. On the other hand, immigrant visas are less common, and certain types of immigrant visas have annual numerical limitations. However, the most common type of immigrant visa, based on an immediate relative who resides in U.S., is not subject to any numerical limits, as well as permanent residents returning to the U.S., and former American citizens.