adjectival vs adjective

adjectival is not a noun while adjective is a noun.

Word	Noun	Adjective	Verb	Adverb
adjectival	No	Yes	No	No
adjective	Yes	Yes	No	No

As adjectives, adjectival and adjective are synonyms defined as:

adjectival and adjective: of or relating to or functioning as an adjective

adjectival (noun)	adjective (noun)
	a word that expresses an attribute of something
	the word class that qualifies nouns

adjectival (adjective)	adjective (adjective)
of or relating to or functioning as an adjective	relating to court practice and procedure as opposed to the principles of law
	of or relating to or functioning as an adjective