This is primarily a question of credits within the university or college system that you are attending. Every school will identify what course requirements, including credits, are necessary to achieve a major or minor in a particular course of study. A choice of major is required at a defined point in time and may be changed within a certain framework. In general, a minor is not required. Based on your interests, a minor or second major could be selected and the credit requirements for each would be identified. For instance, I started my university studies with a double major in French and Music. I eventually decided that I wanted to spend a junior year abroad program which would impact my major in music. I decided then to accept a minor in music and continue with a major in French. I later went on to get a JD. Students may look at a Major and Minor in different courses of study entirely, based on a more prescribed career path - for instance, someone bound for Medical school but with an interest in languages may elect for a Major in biology and a minor in Spanish. They may find that the Major is important for their graduate studies and that having a minor in Spanish would be useful for special interests (ie working in a hospital that requires bilingual doctors).