(grammar, uncountable) Change in the form of a word (morphologic change) to express different grammatical categories.

(grammar, countable) A noun "inflection" represents a change in form or an affix representing such a change in grammar.

(grammar, countable) Any form produced by such an instance of a change, such as the principal parts for any given stem: any of the declined or conjugated forms that constitute its declension or conjugation.

A change in pitch or tone of voice.

(mathematics) A change in curvature from concave to convex or from convex to concave.

A turning away from a straight course.

(optometry) Diffraction.