1,4-Dioxin (also referred as dioxin or p-dioxin) is a heterocyclic, organic, non-aromatic compound with the chemical formula C₄H₄O₂. There is an isomeric form of 1,4-dioxin, 1,2-dioxin (or o-dioxin). 1,2-Dioxin is very unstable due to its peroxide-like characteristics. The term “dioxin” is most commonly used for a family of derivatives of dioxin, known as polychlorinated dibenzodioxins (PCDDs).