Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, although it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing.
In most species milk comes out of the mother's nipples; however, the platypus (a non-placental mammal) releases milk through ducts in its abdomen. In only one species of mammal, the Dayak fruit bat, is milk production a normal male function.
Galactopoiesis is the maintenance of milk production. This stage requires prolactin (PRL) and oxytocin.
Newborn infants often produce some witch's milk.
Galactorrhea is milk production unrelated to nursing, it can occur in males and females of many mammal species as result of hormonal imbalances or unusual physiological stimuli.
Read more about Lactation: Purpose, Lactation Without Pregnancy, Induced Lactation, Relactation, Evolution, See Also