Ma'anar ƙamus na kalmar "lactase" wani enzyme ne wanda ƙananan hanji ke samarwa kuma yana da alhakin narkewar lactose, sukari da ake samu a cikin madara da sauran kayan kiwo. Lactase yana rushe lactose zuwa glucose da galactose, wanda za'a iya shiga cikin jini cikin sauƙi. Wasu mutane na iya zama marasa haƙuri da lactose, wanda ke nufin ba sa samar da isasshen lactase don narkar da lactose yadda ya kamata, wanda ke haifar da alamomi kamar kumburi, gas, da gudawa bayan cinye kayan kiwo.