Compulsory

From Latin compulsorius

Full definition of compulsory

1827, A. D. Jr., Edinburgh Medical and Surgical Journal, A. and C. Black, page 212:They are entirely private concerns, established by individual teachers, and attendance upon them is no more compulsory than attendance on our dispensaries.
1996, Ugo Pagano, Democracy and Efficiency in the Economic Enterprise, page 73:Some might agree that membership in the firm is perhaps more compulsory than membership in a municipality, but balk at applying the analogy to the nation.
2013-07-19, Peter Wilby, Finland spreads word on schools, Imagine a country where children do nothing but play until they start compulsory schooling at age seven. Then, without exception, they attend comprehensives until the age of 16. Charging school fees is illegal, and so is sorting pupils into ability groups by streaming or setting.

The ten-dollar fee was compulsory.
Having the power of compulsion; constraining.
Such compulsory measures are limited.

(plural compulsories)

2008, March 22, The Associated Press, French Victory in Ice Dance, Delobel and Schoenfelder failed to win the free dance, but they had built a big lead in the compulsories and the original dance.