The placenta is the organ that grows inside a woman's womb during pregnancy, joined to the baby by the umbilical cord. It is how the baby is fed: the mother's blood and the baby's blood run very close together inside it, so oxygen and food pass across to the baby and waste passes back. It is temporary — it grows only for that pregnancy, and after the baby is born the mother pushes it out too, which is why English has the everyday word 'afterbirth' for the same thing. This is a normal, non-embarrassing word in English. Doctors use it, pregnancy books use it, and ordinary parents say it without lowering their voice. Other animals have one too, and biologists talk about a cow's or a dog's placenta the same way. The plural is 'placentas' in ordinary use, though medical writing sometimes keeps the Latin 'placentae'. Note that English says 'the placenta', with 'the', when talking about a particular pregnancy: 'the placenta was healthy'.