Wet-nursing is a term widely used to describe the practice of an adult nursing a child who is not biologically theirs. However, there are a lot of synonyms for this term used in different cultures and regions around the world. In some places, it's known as cross-nursing or cross-feeding, while others refer to it as milk-siblings or breastmilk sharing. Wet nursing is also sometimes called co-nursing, foster-nursing, or milk kinship. Regardless of what it's called, the practice of wet nursing has been a common cultural norm throughout history and provides an essential lifeline to infants and mothers who need it.