If you have been away from York and would like to return to your undergraduate studies, the process for returning will depend on several factors.
If you were in good academic standing when you suspended your studies, you might be eligible to simply reactivate your record. Visit http://www.registrar.yorku.ca/enrol/reactivate/ The website provides detailed information on how and when you should submit your request. It also outlines possible restrictions.
If you have already graduated and want to take several courses, you could apply for non-degree status. Visit http://www.registrar.yorku.ca/enrol/nondegree/index.htm. Depending on the length of time that you have been away from York, it may be advisable to speak with an advisor before enrolling. Please contact Science Academic Services or your (future) home department to schedule an advising appointment.
If you were not in good academic standing, have attended another post-secondary institution since your York studies, or are interested in doing a second degree, you will need to re-apply through the Admissions Office. Visit http://futurestudents.yorku.ca/. After your readmission, you should schedule an appointment to meet with an academic advisor. Please contact Science Academic Services or your (future) home department to schedule an advising appointment.