Isomorphism-closed subcategory

In category theory, an **isomorphism-closed subcategory** is a subcategory of a given category that is closed under isomorphisms. This means that if an object is in the subcategory, then all objects isomorphic to it are also included in the subcategory. To elaborate further, let \( \mathcal{C} \) be a category and let \( \mathcal{D} \) be a subcategory of \( \mathcal{C} \).