Students, adjuncts, and staff can renew books 3 times, as long as the book has not been placed on hold by someone else. After the third renewal, you will need to return the book so that it doesn't get marked "lost" in the system. At that point, if it's not been placed on hold, you may check it out again.
Faculty have automatic semester loans, and are unable to renew online.
Community borrowers can have up to 5 renewals.