amnios vs amniotic sac

amnios and amniotic sac both are nouns.

Word	Noun	Adjective	Verb	Adverb
amnios	Yes	No	No	No
amniotic sac	Yes	No	No	No

As nouns, amnios and amniotic sac are synonyms defined as:

amnios and amniotic sac: thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)

Other synonyms of amnios include amnion.

amnios (noun)	amniotic sac (noun)
thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)	thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)