Why are the Peano axioms axioms for natural numbers if they have non-standard models?

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Why are the Peano axioms axioms for natural numbers if they have non-standard models? Shouldn't axioms determine an object up to isomorphism?

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The original formulation of Peano-Dedekind axioms corresponds to modern Second Order Logic version.

Richard Dedekind in The Nature and Meaning of Numbers (Was sind und was sollen die Zahlen? (1888)), proved that they characterize the natural numbers up to isomorphism.