Repetition of a word in a different case or inflection in the same sentence

Wikipedia Word definitions in Wikipedia
Polyptoton is the stylistic scheme in which words derived from the same root are repeated (such as "strong" and "strength"). A related stylistic device is antanaclasis , in which the same word is repeated, but each time with a different sense. Another related ...

Wiktionary Word definitions in Wiktionary
n. (context rhetoric English) A stylistic scheme in which words from the same root are used together, or a word is repeated in a different inflection or case.

WordNet Word definitions in WordNet
n. repetition of a word in a different case or inflection in the same sentence; "My own heart's heart"

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Polyptoton \Pol`yp*to"ton\, n. [L., fr. Gr. ? having, or being in, many cases; poly`s many + ? case.] (Rhet.) A figure by which a word is repeated in different forms, cases, numbers, genders, etc., as in Tennyson's line, -- ``My own heart's heart, ...