Agente de limpieza y emulsificante obtenido al hervir un aceite, grasa, resina o cera con un álcali.Een reinigend en emulgerend middel dat wordt verkregen door olie, vet, hars of was te koken met een alkali .一種由水分散的清潔及乳化劑，由長鏈脂肪酸（見於油類和脂肪）與鹼（如氫氧化鈉或鹼液）的皂化作用製成。自古代即啟用以動物脂肪和木灰做成的肥皂。雖然在歐洲中世紀至近代早期間，肥皂是家中為了洗衣而製造的，塊狀肥皂卻是奢侈品，直到十九世紀才被大眾使用。A water-dispersible cleansing and emulsifying agent produced by the saponification reaction of long chain fatty acids, such as found in oils and fats, with an alkali, such as sodium hydroxide or lye. Soaps made from animal fat and wood ashes have been used since antiquity. Although soap was made at home for laundry purposes from the European Middle Ages to early modern times, cake soap was a luxury product that came into common use only in the 19th century.