inflection vs inflectional

inflection is a noun but inflectional is not a noun.

Word	Noun	Adjective	Verb	Adverb
inflection	Yes	No	No	No
inflectional	No	Yes	No	No

inflection (noun)	inflectional (noun)
the patterns of stress and intonation in a language
a manner of speaking in which the loudness or pitch or tone of the voice is modified
deviation from a straight or normal course
a change in the form of a word (usually by adding a suffix) to indicate a change in its grammatical function

inflection (adjective)	inflectional (adjective)
	characterized by inflections indicating grammatical distinctions