What is a visa?

The F-1 or J-1 visa stamp in your passport is permission to apply to enter the United States in that visa category. Canadian citizens are not required to have a visa stamp in the passport to enter the U.S.

The F-1 and J-1 category of visa will allow you to enroll in credit bearing classes at a Student and Exchange Visitor Program approved school in the U.S.  抵达美国的游客.S. 按其他签证类别学习可能得不到批准.   You can refer to this chart to view other classifications and the ability to study under those classifications 

留在美国是可以的.S. after your F-1 or J-1 visa expires as long as your passport and I-20 or DS-2019 are valid, 你是一名全日制学生. The visa expiration date is separate from your length of authorized stay in the U.S.

如果你的签证在美国期间到期.S., the next time you travel internationally you must apply for a new F-1 or J-1 visa in order to return to the U.S. This is also true if your visa has a limited number of entries that have been used, 或者在美国期间更改了非移民身份.S.