Rh factor

\ ˌär-ˈāch- How to pronounce Rh factor (audio) \

Definition of Rh factor

: any of one or more genetically determined antigens present in the red blood cells of most persons and of higher animals and capable of inducing intense immunogenic reactions

First Known Use of Rh factor

1942, in the meaning defined above

History and Etymology for Rh factor

rhesus monkey (in which it was first detected)

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The first known use of Rh factor was in 1942

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Cite this Entry

“Rh factor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/Rh%20factor. Accessed 24 Jan. 2021.

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Rh factor

How to pronounce Rh factor (audio)

English Language Learners Definition of Rh factor

medical : a substance that is present in the red blood cells of most people

Rh factor

\ ˈär-ˈāch- How to pronounce Rh factor (audio) \

Medical Definition of Rh factor

: a genetically determined protein on the red blood cells of some people that is one of the substances used to classify human blood as to compatibility for transfusion and that when present in a fetus but not in the mother causes a serious immunogenic reaction in which the mother produces antibodies that cross the placenta and attack the red blood cells of the fetus

called also rhesus factor

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