What's the difference between agnomination and polyptoton?

Agnomination

Definition:

• (n.) A surname.
• (n.) Paronomasia; also, alliteration; annomination.

Example Sentences:

Polyptoton

Definition:

• (n.) 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, and ownest own, farewell."

Example Sentences: