i Register
In some senses, extracurricular is marked as informal. Watch for register when choosing this word.
adj
Outside of the normal curriculum of an educational establishment.
The students enjoy a number of extracurricular activities at weekends.
Similarly outside of the normal duties of a job or profession.
Extramarital.
noun
An activity outside the normal academic curriculum.
An activity beyond official duties of a job or profession.
An extramarital affair.