inflection vs flexion

inflection and flexion both are nouns.

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

As nouns, inflection and flexion are synonyms defined as:

Other synonyms of inflection include flection.

inflection (noun)	flexion (noun)
the patterns of stress and intonation in a language	act of bending a joint; especially a joint between the bones of a limb so that the angle between them is decreased
a manner of speaking in which the loudness or pitch or tone of the voice is modified	deviation from a straight or normal course
deviation from a straight or normal course	the state of being flexed (as of a joint)
a change in the form of a word (usually by adding a suffix) to indicate a change in its grammatical function