Independent Activities Period. MIT has a fairly unusual system, in that rather being quarterly or semesterly, it goes on a 4-1-4 schedule, which means our fall term ends in December, and our spring term does not begin til February. What do we do in January? That's IAP. You can do whatever you want. Despite the lack of any formal structure, there's a phenomenal number of activities going on, from short-term intensive classes offered by departments, to the other end of the spectrum with paper-airplane contests. It's the one time of the year where you can be at MIT with all of your friends and not be totally stressed about classes. Very nice. I hope it never goes away despite certain faculty initiatives to cancel it.