suspiciousness vs suspicious

suspiciousness is a noun but suspicious is not a noun.

Word	Noun	Adjective	Verb	Adverb
suspiciousness	Yes	No	No	No
suspicious	No	Yes	No	No

suspiciousness (noun)	suspicious (noun)
being of a suspicious nature

suspiciousness (adjective)	suspicious (adjective)
	openly distrustful and unwilling to confide
	not as expected