This is the iron-salt-dependent decomposition of dihydrogen peroxide, generating the highly reactive hydroxyl radical, possibly via an oxoiron(IV) intermediate. Addition of a reducing agent, such as ascorbate, leads to a cycle which increases the damage to biological molecules. The transformation of this definition into the Aristotelian structure would be: A chemical reaction that is "the ironsalt-dependent decomposition of dihydrogen peroxide, generating the highly reactive hydroxyl radical, possibly via an oxoiron(IV) intermediate" and that is typically represented by the reaction formula: F e 2+ + H 2 O 2 → F e 3+ + OH • +OH -. This definition suffices to declare the class it defines as being a subclass of the chemical reaction class within our ontology.