| a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes. |
| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| Rh factor | |
| —n | |
| Rh positive See also Rh negative Full name: rhesus factor an agglutinogen commonly found in human blood: it may cause a haemolytic reaction, esp during pregnancy or following transfusion of blood that does not contain this agglutinogen | |
| [C20: named after the rhesus monkey, in which it was first discovered] | |
| Rh positive | |
| —n | |
| 1. | blood containing the Rh factor |
| 2. | a person having such blood |
Rh factor n.
Any of several substances on the surface of red blood cells that induce a strong antigenic response in individuals lacking the substance.
| Rh factor (är'āch') Pronunciation Key
Any of several antigens present on the surface of red blood cells in most humans. People with Rh factors are classified as having a blood type that is Rh positive, while people who lack the antigen are said to be Rh negative and can produce powerful antibodies that destroy red blood cells if given a blood transfusion from an Rh-positive donor. A woman who is Rh negative and is pregnant with an Rh-positive fetus can produce antibodies that are life threatening to the fetus. See Note at blood type. |
Any of several substances found on the surface of red blood cells in persons.
Note: An Rh-negative woman who gives birth to an Rh-positive baby may develop antibodies to the Rh factor during her first pregnancy. These antibodies may cause a disorder in Rh-positive babies conceived afterward that could result in the death of the infant if the condition is not recognized and treated.