Special student 应该不只是undergraduate 的吧:
这是OU关于special student的定义:
A special student is a student who registers for courses for personal interest without seeking a degree. In such a case, formal admission to a program of study is not necessary. Accumulated credits as a special student ?to a maximum of 30 ?can be retained for eventual admission to a program of study.
Special students are subject to the same general and faculty regulations as regular students concerning attendance at courses, assignments, examinations, grading, academic fraud, appeals, payment of fees, etc.