Ma'anar ƙamus na fermentation shine rushewar sinadari na wani abu ta hanyar ƙwayoyin cuta, kamar yisti ko ƙwayoyin cuta, zuwa abubuwa masu sauƙi, yawanci tare da juyin halitta na gas da zafi. Wani tsari ne na rayuwa wanda ke faruwa idan babu iskar oxygen, kuma ana amfani da shi wajen samar da abubuwan sha, burodi, yogurt, da sauran abinci. A lokacin fermentation, sugars suna canza zuwa barasa ko Organic acid, wanda zai iya ba da dandano na musamman da laushi zuwa samfurin ƙarshe.