WordNet sense 1 (a change in the form of a word (usually by adding a suffix) to indicate a change in its grammatical function):

inflexion

WordNet sense 2 (deviation from a straight or normal course):

flection, flexion

WordNet sense 3 (a manner of speaking in which the loudness or pitch or tone of the voice is modified):

modulation

WordNet sense 4 (the patterns of stress and intonation in a language):

prosody