<p>Hi Olive_Tree, great question!</p>
<p>It's a simple system, but it does have some rules that are good to know, so I'll walk through them.</p>
<p>First of all, almost irrelevantly, they're not called majors or minors, they're called "concentrations" and "secondary fields." (I know, it's a little odd).</p>
<p>A list of the undergraduate concentrations is here:</p>
<p>FAS</a> Handbook for Students: Chapter 3: Fields of Concentration</p>
<p>You must pick at least one concentration, and you do so in the middle of your sophomore year (deadline for last year was something like December 3). You have a lot of great help and advising along the way, both from your house advisers and from the concentration tutors.</p>
<p>You can decide to do a joint concentration between two (no more than two!) concentrations. For example, you could try Physics + Philosophy, if that's what you're into. Joint concentrations aren't too rare but they must be approved by the concentration tutor (if you have a good explanation of why you'd like to do a joint concentration, you'll probably be allowed to do one).</p>
<p>Two things to note: Joint concentrations have a primary and a secondary field (the difference between Physics + Philosophy and Philosophy + Physics), and joint concentrations are normally honors concentrations that culminate in a senior thesis. Therefore, if you pick a joint concentration, make sure you're willing to write a thesis that combines the two disciplines.</p>
<p>One issue is that some departments don't allow you to do a joint concentration. Most prominently, Economics and Psychology (two of the three largest concentrations) just recently announced they would no longer participate in joint concentrations. Each concentration has a different policy on this- look at their page on the website above, and you can see both whether they allow joint concentrations and how popular a joint concentration is (look at the table on the bottom of the page).</p>
<p>If you wish to change your concentration after declaring it, you can (it just requires a couple of signatures). This obviously gets more difficult the later you wait (it would usually happen sometime junior year), since you have to catch up on courses you missed.</p>
<p>That's enough about the main concentrations. As for secondary fields, the most helpful site is here:</p>
<p>Secondary</a> Fields</p>
<p>There you can find frequently asked questions and a list of secondary fields, as well as their requirements. The basic summary:</p>
<p>Secondary fields are not rare, but they are completely optional- they are not required or expected of students. You are not permitted to have more than one secondary field.</p>
<p>Secondary fields each require either 4, 5, or 6 courses. Each secondary field has its own requirements for what courses can be taken to satisfy it- they could be general (allowing you to take any courses in the department) or specific (requiring a couple of key courses, for example). See the list of programs for details on each secondary field.</p>
<p>Secondary</a> Fields: List of Current Programs</p>
<p>Finally, you can "double count" only one course. That is, you can use only one course to count towards both your concentration or core requirements and your secondary field. So I can count CS 50 towards both my Stat concentration and my CS secondary field, but once I have I cannot also count CS 51 towards both.</p>
<p>I hope I've made the process clear. If you have any questions please don't hesitate to ask. Are there specific concentrations you're interested in, or particular concerns you have about the process?</p>
<p>Incidentally, I'm afraid I don't really know anything about the Extension school, if that's what you meant by the undergraduate degree programs.</p>