What a minor is
A minor is a secondary, formally recognized area of study alongside your major — usually 15–18 credits, open to any undergraduate whose major is in a different field. It shows up on your transcript and diploma, but not as a separate degree. Some minor courses may also satisfy general-education or major requirements; check with your adviser and your degree audit.
How to declare
Declaring a minor is a form in MyPorter, usually with your adviser's sign-off — there is no separate application or admission decision the way there can be for some majors. Most students declare by the start of their junior year so the courses fit into remaining terms without adding time to graduation.
Fitting it in
A minor works best when its courses overlap with electives you would take anyway, or when it pairs naturally with your major (a business minor alongside an engineering major, for instance). Run a minor's representative courses past your adviser before declaring to see how many terms it actually adds, if any.