Essential; crucial; extremely important.
Having semantics that incorporates mutable variables.
Expressing a command; authoritatively or absolutely directive.
Of, or relating to the imperative mood.
A verb in imperative mood.
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.
An essential action, a must: something which is imperative.
Of critical importance to the success of a particular endeavor.
Having death as a possible or even likely outcome; perilous.
Of critical importance to the survival of a living organism.