Merriam-Webster Logo
SINCE 1828
Menu
×

An Encyclopædia Britannica Company

amnion

play
noun am·ni·on \ˈam-nē-ˌän, -ən\

Definition of amnion

plural

amnions

or

amnia

play \-nē-ə\

  1. 1 :  a thin membrane forming a closed sac about the embryos or fetuses of reptiles, birds, and mammals and containing the amniotic fluid

  2. 2 :  a membrane analogous to the amnion and occurring in various invertebrates

amniotic

play \ˌam-nē-ˈä-tik\ adjective

See amnion defined for kids

From the M-W Editors

alt-59760690a61d7
Trending: Trump Tweets, We Define: 'Beleaguered'
video-title-words-of-the-year-1066
Words of the Year: 1066
image386126722
Words That Come From the Dinner Table
emoji-the-quiz
The Emoji Quiz

Origin and Etymology of amnion

New Latin, from Greek, caul, from amnos lamb — more at yean

Medical Dictionary

amnion

play
noun am·ni·on \ˈam-nē-ˌän, -ən\

Medical Definition of amnion

plural

amnions

or

amnia

\-nē-ə\play

  1. :  a thin membrane forming a closed sac about the embryos and fetuses of reptiles, birds, and mammals and containing the amniotic fluid—called also amniotic sac

Learn More about amnion

  1. See words that rhyme with amnion Britannica.com: Encyclopedia article about amnion

Seen and Heard

What made you want to look up amnion? Please tell us where you read or heard it (including the quote, if possible).

show hide

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

haphazard

play

marked by lack of plan or order

Get Word of the Day daily email!

TRENDING NOW

  1. beleaguer 'Being subjected to constant or repeated trouble or harassment'

  2. scaramouch A new White House communications director

  3. non sequitur “It does not follow”

  4. admiral's mast A massive search ends with an 'admiral's mast'.

  5. calumny 'An untrue statement that is made to damage someone's reputation'

SEE ALL

BROWSE DICTIONARY

amnion

Test Your Vocabulary

The Emoji Quiz

  • emoji-the-quiz
  • What phase of the moon is this: 🌖 ?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
Dictionary Devil

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play

alt-596f95fe451e7
'Drought' & 'Drouth' Take Us Back In Time

A variant spelling with a long history

alt-59721dd897313
The 'Best' Way to Sign Off On An E-mail

Give them your best

image386126722
Words and Phrases That Come from the Dinner Table

Fill your plate with these surprising food words

ghost-being-disinvited-from-party
'Disinvite' or 'Uninvite'?

A disinvited guest is an uninvited problem

Ask the Editors

video-title-words-of-the-year-1066
Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

payday
How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless
Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals
Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

emoji-the-quiz
The Emoji Quiz

Think you’re an emoji 👓 expert? Let’s see 🤔

Take the quiz
image941935269
A Game of Thrones Word Quiz

In the Game of Thrones quiz, you learn some new vocabulary. (It’s quite safe, really. You will not die.)

Take the quiz
Name That Thing
Name That Thing

Test your visual vocabulary with our 10-question challenge!

Take the quiz
Dictionary Devil
Dictionary Devil

The dictionary has been scrambled—can you put it back together?

Play the game