As a non-US national I never really know what a "semester" is with respect to US universities. Not sure what a better title would be though. The key information here in my opinion is that students are being told not o come back in a few weeks following spring break.

U.S universities typically have two sessions per year: the "fall semester" (usually September-December) and the "spring semester" (usually January-May). Each course (e.g., Introduction to Chemistry) typically runs one semester. A full-time student usually studies 3-4 courses per semester.

Many universities also offer a small number of courses during the summer break. Some universities allow certain courses to be only a half-semester in duration.

Many universities (but not MIT) are on a quarter system. I honestly don't know which one is more prevalent.

I suppose we could say "term" but it starts to feel like diminishing returns.