Definition from Wiktionary, the free dictionary
- (rhetoric) A stylistic scheme in which words from the same root are used together, or a word is repeated in a different inflection or case.
Usage notes 
An example of polyptoton appears in the following quote with variation on the word feed:
- c1595, William Shakespeare, s:Richard II, act II, scene i,
- With eager feeding food doth choke the feeder.
- (rhetoric): ploce