cross-sectional vs cross section

cross-sectional is not a noun while cross section is a noun.

Word	Noun	Adjective	Verb	Adverb
cross-sectional	No	Yes	No	No
cross section	Yes	No	No	No

cross-sectional (noun)	cross section (noun)
	(physics) the probability that a particular interaction (as capture or ionization) will take place between particles; measured in barns
	a sample meant to be representative of a whole population
	a section created by a plane cutting a solid perpendicular to its longest axis

cross-sectional (adjective)	cross section (adjective)
of or relating to a cross section
representing a plane made by cutting across something at right angles to its length