A 12 month period of employment authorization that a student may take during schools breaks, while school is in session, after completion of all course requirements except a thesis or dissertation or after completion of studies. Employment may be full or part-time, but must be part-time if the student is still attending classes. OPT must be approved by USCIS before the student can commence employment. Any student who works for one year or more in full-time curricular practical training is not eligible for optional practical training.