Milk-secreting organ of female mammals; SYN. mamma.
In female mammals, a milk-producing gland derived from epithelial cells underlying the skin, active only after the production of young. In all but monotremes (egg-laying mammals), the mammary glands terminate in teats which aid infant suckling. The number of glands and their position vary between species. In humans there are 2, in cows 4, and in pigs between 10 and 14.
The hatched young of monotremes simply lick milk from a specialized area of skin on the mother's abdomen.