# Coercion

Structure does type coercion based on the declared [schema](/v1/schema-concept.md). It's important to note that it **never** coerces the following scenarios:

* `undefined`;
* `null` when `nullable` option is enabled;
* value is already of the declared type (except for arrays, we'll talk more about this soon).

Let's break the coercion into 3 categories.


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