(noun)
the authority to carry out a particular course of action or enact a particular policy, granted to a representative, especially to someone who has won an election;
e.g. The candidate respected the mandate of the citizens and developed the policy to benefit them.
(noun)
in historical usage, an official command given by the League of Nations to a member country, for establishing government and taking over administration in conquered territories;
e.g. The mandate established a new government in the state.
(verb)
to officially order or require something, i.e. to make it mandatory;
e.g. The terms of your contract mandate your attendance at this event.
(verb)
to officially require or direct someone to do something, especially to assign them a responsibility;
e.g. The new law will mandate them to have sole power over this territory.