adjective
Essential; crucial; extremely important.
(grammar) Of, or relating to the imperative mood.
(computing theory) Having semantics that incorporates mutable variables.
Expressing a command; authoritatively or absolutely directive.
noun
(uncountable, grammar) The grammatical mood expressing an order (see jussive). In English, the imperative form of a verb is the same as that of the bare infinitive.
(countable, grammar) A verb in the imperative mood.
(countable) An essential action, a must: something which is imperative.