imperative vs shrill

imperative is a noun but shrill is not a noun.

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

imperative (noun)	shrill (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

imperative (adjective)	shrill (adjective)
requiring attention or action	of colors that are bright and gaudy
relating to verbs in the imperative mood	having or emitting a high-pitched and sharp tone or tones
	being sharply insistent on being heard

imperative (verb)	shrill (verb)
	utter a shrill cry