Mandatory (adjective)
Obligatory; required or commanded by authority.
“Attendance at a school is usually mandatory for children.”
Mandatory (adjective)
Of, being or relating to a mandate.
“Mandatory Palestine”
Mandatory (noun)
A person, organisation or state who receives a mandate; a mandatary.
Mandatorily (adverb)
In a mandatory manner; not optionally; required.
Wiktionary
Mandatory (adjective)
required by law or mandate; compulsory
“wearing helmets was made mandatory for pedal cyclists”
Mandatory (adjective)
of or conveying a command
“he did not want the guidelines to be mandatory”
Mandatory (noun)
variant spelling of mandatary
Oxford Dictionary