SINCE 1828
dictionary
thesaurus

Rh factor

noun
Save Word
\ 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)

Learn More About Rh factor

Time Traveler for Rh factor

Time Traveler

The first known use of Rh factor was in 1942

See more words from the same year

Dictionary Entries Near Rh factor

rhexia

Rh factor

RHI

See More Nearby Entries 

Statistics for Rh factor

Cite this Entry

“Rh factor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/Rh%20factor. Accessed 19 May. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for Rh factor

Rh factor

noun
\ 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

WORD OF THE DAY

kibosh

Listen to the pronunciation of kibosh

See Definitions and Examples »

Test Your Vocabulary

Name That Food

  • a-light
  • Name these cookies!
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Universal Daily Crossword

A daily challenge for crossword fanatics.

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
Ask the Editors
Word Games