inflection

Concise Oxford English Dictionary © 2008 Oxford University Press:
inflection /ɪnˈflekʃn/ (chiefly Brit. also inflexion)

▶noun

• 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.

• 2 the modulation of intonation or pitch.

• 3 chiefly Mathematics a change of curvature from convex to concave.

– derivatives
inflectional adjective,
inflectionally adverb,
inflectionless adjective.