A contraction of reduction-oxidation, a type of chemical reaction in which one reactant is reduced (gains electrons) while the other is oxidized (loses electrons). Examples of redox mud chemistry are: (1) sulfite anions to remove molecular oxygen, (2) sulfide removal by oxygen or peroxide, (3) air oxidation of lignite to create more humic acid, (4) sulfate reducing bacteria that generate sulfide ions by biological redox reactions, (5) chromate ions being converted to chromic ion in a mud system.