combinatorial vs combination

combinatorial is not a noun while combination is a noun.

Word	Noun	Adjective	Verb	Adverb
combinatorial	No	Yes	No	No
combination	Yes	No	No	No

combinatorial (noun)	combination (noun)
	the act of combining things to form a new whole
	the act of arranging elements into specified groups without regard to order
	a collection of things that have been combined; an assemblage of separate parts or qualities
	a group of people (often temporary) having a common purpose
	a sequence of numbers or letters that opens a combination lock
	an alliance of people or corporations or countries for a special purpose (formerly to achieve some antisocial end but now for general political or economic purposes)
	a coordinated sequence of chess moves

combinatorial (adjective)	combination (adjective)
relating to the combination and arrangement of elements in sets
relating to or involving combinations