Amnions are membranes that protect the developing fetus during pregnancy. However, there are several synonyms that can be used to describe these membranes in scientific and medical contexts. One synonym is "amniotic sac," which refers to the thin-walled, fluid-filled sac that surrounds the fetus and forms from the amnion. Another synonym is "chorion," which is the outermost membrane that encloses the amnion and fetus. Additionally, the term "decidua" can be used to describe the thickened lining of the uterus that forms during pregnancy and surrounds the amniotic sac. Overall, understanding these synonyms for amnions can help in describing the complex anatomy and physiology of pregnancy.