adjective
compulsory
kuhm-PUHL-suh-ree/kəmˈpʌlsəri/
Required by a rule, law, or authority.
Wearing a hard hat is compulsory before the worker enters the construction site.

Etymology
The pieces lead to the idea of driving together or forcing. Something compulsory is done under compulsion: a rule or authority requires it rather than leaving it to choice.
In context
a very common law at the time which was compulsory sterilization of people who are judged adjudicated to be feeble-minded
More examples
- School attendance is compulsory until a certain age.
- The university makes a writing course compulsory for first-year students.
- Military service is compulsory in some countries.
Forms
compulsory
compulsion noun — The act of forcing someone to comply.
Similar words
- mandatory
- Often emphasizes a requirement imposed by an official authority.
- obligatory
- Can also describe duties arising from custom or social expectations.