Numerous legal disciplines are combined in novel ways to form the field of sports law. Antitrust, contract and tort issues arise frequently. The categories of amateur, professional, and international sports can be used to categorize sports law. It can be difficult to tell a professional athlete apart from an amateur athlete. At universities, so-called "amateur" student-athletes frequently receive financial aid and other types of payment. Additionally, bear in mind that while one organization may define an athlete as an amateur, another organization may not agree. This naturally causes even more confusion. An easy-to-understand yet helpful distinction is that amateur athletes engage in sports as a hobby, whereas professional athletes do so as their job.