Rh factor

noun

ˌär-ˈāch- 

: 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

Word History

Etymology

rhesus monkey (in which it was first detected)

First Known Use

1942, in the meaning defined above

Kids Definition

Rh factor

noun

är-ˈāch- 

: a 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 the mother causes a serious condition in which the mother produces antibodies that cross the placenta and attack the red blood cells of the fetus

Etymology

from rhesus monkey, the animal in which the Rh factor was found

Medical Definition

Rh factor

noun

ˈär-ˈāch- 

: 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