- the innermost membrane of the sac enclosing the embryo of a mammal, reptile, or bird: it is filled with a watery fluid (amniotic fluid)
- a similar membrane of certain invertebrates, esp. insects
Origin of amnionGr, diminutive of amnos, lamb ; from Indo-European an unverified form agwhnos from source yean, Classical Latin agnus
nounpl. am·ni·ons or am·ni·a
Origin of amnionGreek amniōn.
- am′ni·ot′ic , am′ni·on′ic
(plural amnions or amnia)
From Latin amnion (“membrane around a fetus”), from Ancient Greek [script?] (amnion, “bowl in which the blood of victims was caught”), from [script?] (ame, “bucket”).