Definition of "compulsory"

They are entirely private concerns, established by individual teachers, and attendance upon them is no more compulsory than attendance on our dispensaries.

1827, A. D. Jr., Edinburgh Medical and Surgical Journal, A. and C. Black, page 212

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.

1996, Ugo Pagano, Democracy and Efficiency in the Economic Enterprise, page 73

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.

2013 July 19, Peter Wilby, “Finland spreads word on schools”, in The Guardian Weekly, volume 189, number 6, page 30

I haven't booked, so I don't have a clue as to whether the service will be busy or not. Supposedly, reservations are compulsory, but I want to find out what would happen if you just turn up.

2020 December 2, Paul Bigland, “My weirdest and wackiest Rover yet”, in Rail, page 68

Delobel and Schoenfelder failed to win the free dance, but they had built a big lead in the compulsories and the original dance.

2008 March 22, The Associated Press, “French Victory in Ice Dance”, in New York Times‎