noun
elective class; optional course
Refers to a class or course that students can choose to take, as opposed to a required class.
来学期は選択授業で心理学を取るつもりです。
Next semester I plan to take psychology as an elective class.
必修科目 is a required subject, while 選択授業 is an elective class.
Compound of 選択 (selection, choice) and 授業 (class, lesson).