Formalin wani bayani ne bayyananne, mara launi, kuma mai ƙaƙƙarfan ƙamshi wanda yawanci ya ƙunshi kusan kashi 37% na iskar formaldehyde wanda aka narkar da shi cikin ruwa, tare da ƙaramin adadin methanol mai daidaitawa. Formalin yawanci ana amfani dashi azaman maganin kashe kwayoyin cuta da abubuwan kiyayewa, musamman a fannin likitanci da kimiyya. Ana kuma amfani da ita wajen yin kawanya don adana gawar mutane da dabbobi. Ana amfani da kalmar "formalin" sau da yawa tare da "formaldehyde mafita."