Are you asking about everything you will need? Or just academic supplies? Also, what you need will depend on what university and courses, along with where you will be staying (dorm, host family, short-term apartment, etc.) The basics listed by Steve and Neal are accurate, but some (like a graphing calculator) are course specific. You can message me if you want a better idea of things like appropriate clothing or such. Just let me know what university you will be visiting and I can try to help.

a dictionary

A nice backpack to hold your books, a laptop, graphing calculator, pencils, pens, notebooks