cho·​ri·​on | \ ˈkȯr-ē-ˌän How to pronounce chorion (audio) \

Definition of chorion

: the highly vascular outer embryonic membrane of reptiles, birds, and mammals that in placental mammals is associated with the allantois in the formation of the placenta

Examples of chorion in a Sentence

Recent Examples on the Web This is essentially a blood clot that can occur when the outermost membrane surrounding the embryo (the chorion) separates a little from the uterine wall, allowing some blood to pool in that space between the two. Amy Marturana, SELF, "12 Causes of Spotting and Breakthrough Bleeding," 28 Dec. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'chorion.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of chorion

1545, in the meaning defined above

History and Etymology for chorion

New Latin, from Greek, afterbirth

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Time Traveler for chorion

Time Traveler

The first known use of chorion was in 1545

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Cite this Entry

“Chorion.” Dictionary, Merriam-Webster, Accessed 11 Apr. 2021.

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More Definitions for chorion


cho·​ri·​on | \ ˈkōr-ē-ˌän, ˈkȯr- How to pronounce chorion (audio) \

Medical Definition of chorion

: the highly vascular outer embryonic membrane that is associated with the allantois in the formation of the placenta

More from Merriam-Webster on chorion

Britannica English: Translation of chorion for Arabic Speakers Encyclopedia article about chorion

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