1 Grammar a change in the form of a word (typically the ending) to express a grammatical function or attribute such as tense, mood, person, number, case, and gender:a set of word forms differing only in respect of inflections
[mass noun] the process or practice of inflecting words.
2 [mass noun] the modulation of intonation or pitch in the voice:she spoke slowly and without inflection [count noun]:the variety of his vocal inflections
the variation of the pitch of a musical note.
3chiefly Mathematics a change of curvature from convex to concave at a particular point on a curve:the point of inflection of the bell-shaped curve