cortex vs cortical

cortex is a noun but cortical is not a noun.

Word	Noun	Adjective	Verb	Adverb
cortex	Yes	No	No	No
cortical	No	Yes	No	No

cortex (noun)	cortical (noun)
the tissue forming the outer layer of an organ or structure in plant or animal
the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
the tissue that surrounds the lens nucleus

cortex (adjective)	cortical (adjective)
	of or relating to a cortex