amnion /amˈni-ən/ noun (pl amˈnia) The innermost membrane enveloping the embryo of reptiles, birds and mammals ORIGIN: Gr amˈniote noun Any vertebrate animal that possesses an amnion, chorion and allantois during fetal development amniotˈic adjective amniotic cavity noun The space between the embryo and the amnion amniotic fluid noun The fluid within the amnion in which the embryo is suspended |