peremptory vs imperative

peremptory is not a noun while imperative is a noun.

Word	Noun	Adjective	Verb	Adverb
peremptory	No	Yes	No	No
imperative	Yes	Yes	No	No

peremptory (noun)	imperative (noun)
	some duty that is essential and urgent
	a verb in the imperative mood.
	a mood that expresses an intention to influence the listener's behavior

peremptory (adjective)	imperative (adjective)
putting an end to all debate or action	requiring attention or action
offensively self-assured or given to exercising usually unwarranted power	relating to verbs in the imperative mood
not allowing contradiction or refusal