PhD opportunities in Spring in US universities I am facing a dilemma regarding whether or not to apply for Spring for PhD programs at some universities in US. What are the pros and cons of applying for PhD or MS programs in Spring?
Most PhD programs, and many master's programs, in the US only offer one admissions cycle per year, with programs starting in the fall. This is in part because of the PhD program encompassing classwork as well as research.

The main issue that speaks against spring admissions is that in most programs, the coursework begins in the fall semester, and any "sequences" (where course Y depends on course X) will often begin in the fall semester. Thus, starting in the spring semester may mean that your coursework phase will need to extend longer, so there's no real advantage between starting in the spring and waiting until the following fall.

Where there might be an advantage is if you are able to use some of the time for finding a research group (if that is necessary for a research thesis for the master's degree); in some cases, you could even get a head start on the thesis work, which could allow you to finish somewhat faster.