decompositional vs decomposition

decompositional is not a noun while decomposition is a noun.

Word	Noun	Adjective	Verb	Adverb
decompositional	No	Yes	No	No
decomposition	Yes	No	No	No

decompositional (noun)	decomposition (noun)
	the analysis of a vector field
	the organic phenomenon of rotting
	(biology) the process of decay caused by bacterial or fungal action
	(chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance
	in a decomposed state

decompositional (adjective)	decomposition (adjective)
causing organic decay